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SECTION I
INTRODUCTION
1.1 SCOPE
This instruction manual contains inforination necessary for the installation, operation and maintenance of the transceiver.
1.2 DESCRIPTION
The transceiver is a compact, rugged military-type 120 watt transceiver covering 1.6000 MHz to 29.0000 MHZ. The transceiver can operate either simplex or half-duplex in channelized node or simplex in frequency mode. Ten half-duplex channels, storing frequencies and modes are available and may be programmed from the front panel. Receive and transmit modes are AME (upper sideband with full carrier), CW (1 kHz keyed tone), USB, LSB and FSK (RITY or FAX with additional modems). The transceiver is mechanically and electrically designed and packaged to meet military specifications for vibration, shock and environment. The transceiver is sealed against dust and spray, making it ideal for for exposed mobile as well as base station installations. The transceiver can operate in temperatures from -30°C to +65°C and in 0 to 95% relative humidity.
The transceiver has been designed and constructed to facilitate quick and easy field service and/or repair. Featuring modular construction, the front panel, rear panel, and power amplifier assemblies are removeable with only a screwdriver and the PC boards simply unplug from the mother board.
The transceiver is composed of eight major subassemblies. A general de
scription and function of these assemblies are provided in Sections 1.2.2 through 1.2.9 and the location of these subassemblies can be found in Figure 1.1.
1.2.2 CHASSIS/MOTHER BOARD
All subassemblies in the transceiver are electrically or mechanically connected to the chassis/mother board. The chassis houses all plugin PC boards and provides shielding. The mother board contains all interconnecting wiring in the transceiver. All plug-in PC boards connect to the mother board through PC edge connectors. Keys on the connectors discourage plugging PC boards in the wrong slots.
1.2.3 FRONT PANEL ASSEMBLY
The front panel is a rugged aluminum casting to which all controls are mounted. The control shafts are sealed against water and dust entry and the speaker is waterproof. The LED displays and display driver circuitry are mounted on the front panel board which attaches to the panel. The panel assembly can be removed by removing four screws and two ribbon cable connectors.
1.2.4 LOGIC BOARD
The logic board contains the microprocessor, memory and transceiver control logic and the coupler interface logic. The transceiver channel memory is a CMOS type which is kept alive by a lithium battery with a 10 year typical life. Signals from the logic board provide frequency information to the synthesizer and band and mode information to the receiver/exciter modules.
1.2.5 RECEIVER /EXCITER
The receiver/exciter consists of eight PC boards: (1) speaker driver, (2) transmit nodulator, (3) audio/ squelch, (4) IF filter, (5) mixer, (6) high pass filter, (7) halfoctave filter and (8) noise blanker.
In the transmit mode, the receiver/ exciter takes inputs from the microphone or other source and the synthesizer, then generates the proper signal to drive the power amplifier (PA). In the receive mode, the receiver/exciter path processes the received signal from the antenna to the speaker, using inputs from the synthesizer.
A double conversion scheme is used, with the first intermediate frequency (IF) at 59.53 MHz and the second IF at 5.00 MHz. Two sets of crystal filters (one set at each IF) determine the radio bandwidth.
A signal compressor on the transmit modulator board improves the peakto-average power ratio for more effective communications.
The squelch circuit on the audio/ squelch board is voice-frequency activated. This reduces random breaking and is designed so that strong signals (>30 UV) will break the squelch regardless of the control position. The noise blanker helps remove vehicle ignition interference while receiving. It may be activated as needed by pulling out the squelch control.
1.2.6 SYNTHESIZER
The synthesizer consists of four PC boards: (1) major loop, (2) translator loop, (3) minor loop and (4) reference board. The synthesizer is a three loop design which provides
the receiver/exciter with the first local oscillator (LO) from the major loop board, the second LO from the translator loop board and the third LO from the reference board to the receiver/exciter. All frequencies are derived from a temperature compensated crystal oscillator (TCXO) on the reference board. The reference board also furnishes the 1 kHz side-tone used for CW. If a fault causes any of the loops to lose lock, the loss-of-lock LED will light on the appropriate board(s) and transmission and reception will be inhibited. Figure 1.1 shows the locations of the loss-of-lock LEDs and other adjustments.
1.2.7 POWER SUPPLY MODULE
The power supply module furnishes regulated +5 and +9 VDC to the transceiver. The power supply is a switching type for good efficiency and operates from either input voltage of 12 or 24 VDC. This module plugs into the mother board.
1.2.8 REAR PANEL ASSEMBLY
The rear panel assembly is an aluminum casting which contains the PA assembly and various connectors. It attaches to the transceiver chassis with four screws and is easily removable as a unit. Figure 1.l shows the locations of the various rear panel assemblies, connectors and fuse locations.
1.2.9 POWER AMPLIFIER ASSEMBLY
The power amplifier (PA) is a solid state broadband amplifier rated at 125 watts peak envelope power (PEP) and 125 watts average into a 50 ohm load. The unit is cooled by a heatsink on the rear panel and requires an optional blower only when the transceiver is to be used for continuous operation.
The PA is manufactured in two versions, 12 or 24 volts. The operating voltage for the entire transceiver is determined by the PA selection. This means that the transceiver may be easily changed fron one operating voltage to the other, even in the field, by simply changing the PA assembly.
1.3 SPECIFICATIONS
1.3.1 FREQUENCY RANGE
1.6000 MHz to 29.9999 MHz in 100 Hz steps,
1.3.2 CHANNEL STORAGE
10 simplex or half-duplex (field programmable)
1.3.3 FREQUENCY STABILITY
+1 ppm from -30°C to +55°C
1.3.4 OPERATING MODES
USB, LSB (A3J upper and lower),
USB reduced carrier (A3A), AME (A3H), CW (Al), FSK (Fl)
(with PA fan option and modem)
1.3.5 POWER INPUT
12V unit : +13.2V + 10%
Receive: 2A Max.
Transmit: 30A Max.
24V unit : +26.4V + 10%
Receive: 2A Max.
Transmit: 20A Max.
1.3.6 TEMPERATURE RANGE
-30°C to +55°C (to +65°C with reduced performance)
1.3.7 HUMIDITY
95% RH at +50°C
1.3.8 SHOCK
MIT-STD 810C Method 516.2,
Procedure 1, Figure 516.2-2 (with shock mounts)
1.3.9 VIBRATION
MIL-STD 810C Method 514.2,
Figure 514.2-6, Curve V (15 to 200 Hz) (with shock mounts)
1.3.10 ENCLOSURE
MIL-STD 108E, splash proof,
Table II
1.3.11 SIZE
13.2 x 37.3 x 42.2 cm (HxWxD)
5.2 x 14.7 x 16.6 in (HxWxD) including handles and heat sink
1.3.12 WEIGHT
15 kg (33 lbs.)
1.3.13 TRANSMITTER
a) Power Output: 125 watts PEP and average +0.5 dB
b) AME Carrier Power: 35 watts nominal
c) Harmonic Suppression: 45 dB, 50 dB typical
d) IM Distortion: 30 dB below PEP, 33 dB typical
e) Undesired Sideband Sup pression: 50 dB at 1 KHZ
f) Hum and Noise: -50 dB
g) Voice Compression: Average power output increases 1 dB or less for 10 dB increase in audio input (can be disabled by internal strapping if required).
h) Audio Input: 600 ohm balanced, rear panel, -15 to +10 dBm for rated output. Carbon, high or low level dynamic microphone, front panel.
i) Transmitter Audio Response: 6 dB, BW 300- 3 kHz (600 ohm input).
1.3.14 RECEIVER
a) Sensitivity: SSB; 0.5 V for 10 dB S+N/N AM: 3 WV for 10 dB S+N/N
b) Selectivity: 6 dB Down 60 dB Down SSB: 2.7 kHz min 6.0 KHz max AME: 5 to 7 kHz 20 kHz max
c) Audio Output: Speaker: 4W at less than 10% distortion. Phones: 10mw at less than 5% distortion. (10% AM). Rear Panel: 600 ohm balanced, +10 dBm at less than 5% distortion (10% AM).
d) AGC Characteristics: < 3 dB output change for an input change from AGC threshold (Type 10 V) to 1.0 V, USB or LSB. Decay Time: AME, USB, LSB, 500 msec. CW, FSK, 50 msec.
e) IF and Image Rejection: 80 dB
f) External Spurious Response: - 60 dB
g) Internal Spurious Response 99.5% of frequencies below 0,2 V equivalent noise input
h) Clarifier Range: +250 Hz minimum (+ 200 Hz minimum when MSR 6400 Remote Interface Board is installed).
i) Intermodulation (In Band): 30 dB below two equal 0.lv (-7 dBm) signals in 3 kHz bandwidth
j) Intermodulation (Out of Band): 70 dB below two equal 3 mv (-37 dBm) signals
k) Front End Protection: Input will withstand 22V RMS (+40 dB) indefinitely
1.4 EQUIPMENT SUPPLIED
1.4.1 TRANSCEIVER,
- Part Number 690022-000-010 - 12V, Grey 690022-000-01l - 12V, 0.D. 690022-000-012 - 24V, Grey 690022-000-013 - 24V, O.D.
1.4.2 KIT, ACCESSORY
- Part Number 690022-017-001 consisting of:
a) Connector, Audio, MS3106A 20-29P - Part Number 600375-606-006
b) Connector, Accessory, MS3106A 28-21P - Part Num ber 600375-606-004
c) Fuses, 10 Amp, Slo-Blo (5) - Part Number 600006-396033
d) Fuses, 30 Amp, (5) - Part Number 600016-396-046
e) Clamp, Cable for Accessory Connector, (1) - Part Number 600376-606-003
f) Clamp, Cable for Audio Connector - Part Number 600376-606-002
g) Connector, RF, PL-259 - Part Number 600244-606-001
h) Reducer, PL-259 - Part Number 600244-606-002
i) Microphone, Hand - Part Number 600352-713-001
j) Cable, Power - Part Number 600452-540-001
k) Manual, Technical - Part Number 600285-823-001
1.5 OPTIONAL EQUIPMENT
– NOT SUPPLIED
1.5.1 MSR 4020A COUPLER, AUTOMATIC ANTENNA,
- Part Number 600233-800-XXX
1.5.2 SHOCK MOUNT KIT, COUPLER
- Part Number 600233-817-006
1.5.3 SHOCK MOUNT KIT, TRANSCEIVER
- Part Number 600058-700-001
1.5.4 RACK MOUNT KIT, TRANSCEIVER,19"
-Part Number 600059-700001 (Grey)
PN 600059-700-002 Green (0.D.)
1.5.5 MICROPHONE, DESK
- Part Number 600013-386-001
1.5.6 HANDSET, H-250/0
- Part Number 600021-386-001
1.5.7 HEADPHONES, H-251/U
- Part Number 600036-386-001
1.5.8 KEY, CW
- Part Number 600367-616-001
1.5.9 FAN KIT, PA
- Part Number 600072-700-001
1.5.10 POWER SUPPLY, MSR 6214, AC to 12/24 VDC,
- PAN 697007000-001
1.5.11 MSR 6400 REMOTE CONTROL, FULL FUNCTION
- Part Number 699023-000-00X
1.5.12 KIT, DEPOT, SPARE PARTS
- Part Number 600060-700-001
1.5.13 KIT, PC BOARDS, SPARE
– Part Number 600061-700
1.5.14 PA MODULE, SPARE, 24V
– Part Number 600407-705-001
1.5.15 PA MODULE, SPARE, 12V
– Part Number 600407-705-002
1.5.16 CABLE ASSEMBLY RF, WIRED, RG58 ANU WITH UHF MALE (PL259) AND TYPE "N" MALE (UG-536) CONNECTOR - Part Number
600491-540-001 - 10 Ft.
600491-540-002 - 20 Ft.
600491-540-003 - 30 Ft.
600491-540-004 - 40 Ft.
600491-540-005 - 50 Ft.
600491-540-006 - 75 Ft.
600491-540-007 - 100 Ft.
1.5.17 CABLE, RF, RG-58 A/U (SPECIFY LENGTH)
- Part Number 600016102-001
1.5.18 CABLE ASSEMBLY RF, WIRE, RG213U WITH UHF MALE (PL259) AND TYPE "N" MALE (UG-21D/U) CONNECTORS
- Part Number
600492-540-001 - 10 Ft.
600492-540-002 - 20 Ft.
600492-540-003 - 30 Ft.
600492-540-004 - 40 Ft.
600492-540-005 - 50 Ft.
600492-540-006 - 75 Ft.
600492-540-007 - 100 Ft.
600492-540-008 - 150 Ft.
600492-540-009 - 200 Ft.
1.5.19 CABLE, RE, RG-213U (SPECIFY LENGTH)
-Part Number 600017102-001 (Recommended for installations of 30 meters (100 feet) or longer)
1.5.20 INTERCONNECT ANTENNA COUPLER, WIRED, CONNECTORS
CABLE ASSEMBLY, WITH-Part Number
600686-540-001 - 10 Ft.
600686-540-002 - 20 Ft.
600686-540-003 - 30 Ft.
600686-540-004 - 40 Ft.
600686-540-005 - 50 Ft.
600686-540-006 - 75 Ft.
600686-540-007 - 100 Ft.
600686-540-008 150 Ft.
600686-540-009 200 Ft.
1.5.21 CABLE, COUPLER CONTROL (SPECIFY LENGTH)
- Part Number 600069-102-009
1.5.22 INTERCONNECT CABLE ASSEMBLY, WIRED, FUNCTION REMOTE CONTROL
- Part Number
600493-540-001 - 10 Ft.
600493-540-002 - 25 Ft.
600493-540-003 - 50 Ft.
600493-540-004 - 150 Ft.
600493-540-005 - 200 Ft.
1.5.23 CABLE, FULL FUNCTION REMOTE CONTROL
- Part Number 600071-102-002
1.5.24 INTERCONNECT CABLE ASSEMBLY, WIRED, AUDIO REMOTE CONTROL
-Part Number
600464-540-001-10 Ft.
600464-540-002-20 Ft.
600464-540-003-30 Ft.
600464-540-004-40 Ft.
600464-540-005-50 Ft.
600464-540-006-75 Ft.
600464-540-007-100 Ft.
600464-540-008-150 Ft.
600464-540-009-200 Ft.
1.5.25 ANTENNA, 9 FOOT WHIP
-Part Number 600015-398-002
1.5.26 ANTENNA, 16 FOOT WHIP
- Part Number 600015-398-001
1.5.27 BUMPER MOUNT, 9-16 FOOT WHIP
- Part Number 600020-398-001
1.5.28 SPRING, HEAVY DUTY BUMPER, 916 FOOT WHIP
-Part Number 600020-398-002
1.5.29 ANTENNA, LESS MOUNT, 23 FOOT WHIP
- Part Number 600019398-001 (Use with 1.5.35 below)
1.5.30 ANTENNA, 23 FOOT WHIP (with flange mount)
- Part Number 600019-398-001
1.5.31 MOUNT, LAYDOWN, 23 FOOT WHIP
- Part Number 600019-398-003 (Use with 1.5.34 below)
1.5.32 ANTENNA, SECTIONALIZED WHIP, 32 FOOT
- Part Number 600018398-001 (Use with 1.5.38 or 1.5.39 below)
1.5.33 ANTENNA, SECTIONALIZED WHIP, 16 FOOT
-Part Number 600018398-009 (Use with 1.5.38 or 1.5.39 below)
1.5.34 MOUNT, FLANGE FOR 16 AND 32 FOOT ANTENNA
-Part Number 600018-398-007 (Use with 1.5.36 and 1.5.37 above)
1.5.35 MOUNT, FEEDTHRU FOR 16 AND 32 FOOT ANTENNA
- Part Number 600018-398-007 (Use with 1.5.36 and 1.5,37 above)
1.5.36 MOUNT, FEEDTHRU FOR 16 FOOT ANTENNA COAX CONNECTIONS WITH HEAVY DUTY SPRING
- Part Number 600036-398-001 (Use with 1.5.37 above)
1.5.37 MOUNT, FLANGE FOR 16 FOOT WITH HEAVY DUTY SPRING
- Part Number 600035-398-001 (Use with 1.5.37 above)
1.5.38 MOUNT, VEHICULAR FOR 16 FOOT ANTENNA WITH FEEDTHRU MOUNT SIDE BRACKET AND ASSOCIATED MOUNTING HARDWARE
- Part Number 600233-817-008 (Use with 1.5.37 above)
1.5.39 RACK MOUNT KIT, MSR 6214
-Part Number 600209-700-001
1.5.40 PC BOARD EXTENDER CARD
– Part Number 601198-536-001 (Two required on certain PC boards)
1.5.41 PC BOARD EXTRACIOR
– Part Number 600268-618-001
1.5.42 DEPOT SPARE PARTS KIT FOR MSR 6214 POWER SUPPLY (12/24V)
- Part Number 600208-700-001
1.5.43 POWER SUPPLY MODULE EXTRACTOR
- Part Number 600270-618-001
1.5.44 26 VOLT DC CONVERTER, RE QUIRED WITH FULL FUNCTION REMOTE FOR 26 VDC OPERATION
- Part Number 600287-537-001
1.5.45 REMOTE OPTION (FACTORY INSTALLED)
- Part Number 600219-700-001, Required when MSR 6400 remote is to be used.
1.5.46 POWER CABLE, MSR 6214
– Part Number 600870-540-001
SECTION 2
INSTALLATION
2.1 GENERAL
This section describes the installation procedure for the transceiver. Included within this section are procedures for unpacking, inspection and, if necessary, reshipping.
2.2 UNPACKING AND INSPECTION
Unpack the transceiver and make certain that all equipment outlined in Section 1.4 is present. Retain the carton and packing materials until the contents have been inspected. If there is evidence of damage, do not attempt to use the equipment. Contact the shipper and file a shipment damage claim.
2.3 RESHIPPING
If return of the transceiver should become necessary, a Returned Material (RM) number must first be obtained from the factory. This number must be clearly marked on the outside of the shipping carton.
2.4 INSTALLATION
Thoroughly plan the transceiver/ coupler/antenna locations and carefully follow the installation considerations given below. Satisfactory system performance depends upon the care and attention taken prior to and during installation.
The protective connector covers installed on the transceiver for shipping, should remain over unused connectors.
2.4.1 INSTALLATION CONSIDERATIONS
2.4.1.1 Antenna Site Location
For optimum characteristics and safety, the antenna should be imounted high enough to clear any surrounding obstructions. The antenna should also be located as far as possible from nearby objects such as power lines, buildings, etc. Figures 2.1 and 2.2 show typical whip and longwire installations.
2.4.1.2 Adequate Ground
Provide the best possible RF ground for the transceiver and the coupler. Use a flat copper strap, 25 ron wide or number 6 gauge or larger wire and connect it to the ground terminal at the rear of the transceiver and on the coupler case. Leads to the ground systein should be as short as possible.
2.4.1.3 Separation
Provide maximum separation between the coupler output (antenna) and the transceiver. The coupler may be mounted up to 61 meters (200 feet) from the transceiver when RG-213U cable is used. For runs under 30 meters (100 feet), RG-58 A/U cable may be used.
NOTE
Transmitters may oscillate if RF power is radiated or conducted into low level stages. Evidence of this condition is erratic or excessive RF output. The cause is the close proximity of the antenna to the transmitter and/or poor RF grounds.
2.4.1.4 Antenna Lead-In
The lead-in from the coupler to the antenna must be insulated for at least 10 kV potential and should not run parallel to metal objects which are bonded to ground. The coupler should be as close as possible to the antenna and never more than 1 meter away, as this will decrease antenna efficiency.
2.4.2 BASE STATION INSTALLATION
The transceiver has rubber feet so it can be placed on a table or desk. The front feet are longer than the rear ones so the transceiver will tilt at a convenient operating angle. It is important to provide adequate ventilation for the heatsink. Clearances on the order of 25 mm on the sides and 50 mm at the top and rear should be provided. See Figure 2.3 for the transceiver outline dimensions. If the heatsink gets too hot, the RF power will cut back automatically. An optional PA fan (see Section 2.7) is necessary for FSK (RITY) operation.
2.4.2.1 Rack Mount Installation (Transceiver)
The transceiver may be conveniently mounted in a standard 19 inch rack, by using the transceiver rack mount kit (P/N 600059–700-XXX). This kit includes a pair of rack slides, associated hardware and side adapter brackets. The transceiver in the rack mounted configuration requires a standard panel space of 13.21 cm (5.2 inches). For rack mounting, the four rubber feet and top cover fasteners are removed from the transceiver. See Figure 2.5 for assembly details.
2.4.2.2 Rack Mount Installation (Power Supply)
The power supply may be mounted inside a standard 19 inch rack by using the power supply rack mount kit (PN 600209-700-001). This kit consists of a mounting plate and the hardware for rack mounting the AC power supply, utilizing if desired, the space immediately behind that of the transceiver. See Figure 2.6 for assembly details.
2.4.3 VEHICULAR INSTALLATION
The transceiver is normally mounted with the optional shock mount kit (600058-700-001) in mobile installations. Figure 2.7 shows a typical system installation in a vehicle.
2.4.3.1 Mounting Shock Rack
The shock rack mounting hole pattern dimensions are shown in Figure 2.8. The screw clearance holes in the isolators are for number 10-32 UNC machine screws. Sixteen (16) machine screws are required for mounting the shock isolators. Refer to Figure 2.8 for the hole locating dimensions for shock isolators.
2.4.3.2 Mounting Radio Rack in Shock
Place the radio on the shock rack with the rubber feet through the cut-out holes. Slide the radio tothe rear of the shock rack so that the two retainers secure the lower bezel, on the rear of the radio. Position the shock rack clamp so lower bezel on that it clamps the the front of the radio. Hand tighten the knob to lock in place, see Figure 2.9. Overall dimensions of the transceiver and shock rack can be obtained from Figure 2.4.
2.4.3.3 Other Installations
It is recommended that the antenna and transceiver be mounted on opposite sides of the vehicle to minimize stray RF pickup, and the transceiver and coupler MUST be well grounded to the vehicle frame.
Vehicle ignition and charging system noise is frequently a problem in mobile installations. Although the noise blanker in the transceiver minimizes ignition interference, it may be necessary to take some noise suppression measures with the vehicle itself.
The following steps can be taken to reduce ignition and charging system noise.
a) Replace standard spark plugs with high resistance spark plugs (before installing high resistance spark plugs, check with the engine manufacturer or authorized dealer to determine the proper type).
b) Replace the spark plug wiring with radio ignition wire (again, check with the manufacturer or dealer to determine the proper type and length).
c) Install a 0.5 microfarad coaxial capacitor (Cornell-Dublier Type NF-10) in series between the ignition switch and primary of the ignition coil to reduce ignition interference (as close as possible to the coil).
d) Run a length of radio ignition wire from the distributor cap to the coil to reduce distributor interference (caused by the rotor in the distributor cap).
e) The generator (or alternator) causes electrical interference which frequently is blamed on the ignition system. Current passing between the brushes and commutator creates arcing which is heard as a whining sound, that varies with changes in engine speed. Install a 0.5 microfarad coaxial capacitor in series with the armature to reduce whining.
f) The voltage regulator may be a mechanically controlled device having breaker contacts. The breaker points create an arc, causing a popping sound in the receiver. This noise seldom aries with changes in engine speed. Install a 0.5 microfarad coaxial capacitor in series with the terminal connections to reduce voltage regulator noise (the coaxial capacitor is inductive and has high attenuation).
CAUTION
Disconnect the battery ground terminal before adding any components to the battery input of the voltage regulator.
2.4.4 MARINE INSTALLATIONS
The transceiver is weather, splash and corrosion resistant, but should not be installed where it is exposed to salt spray. It should be installed in a well ventilated area away from heat sources such as heating vents, etc. The location should be as close as possible to the power source and grounding point.
IT IS RECOMMENDED THAT THE TRANSCEIVER BE SECURELY GROUNDED, as poor grounding can degrade performance. With a metal hull, the transceiver can be grounded directly to the vessel's structure. With a wood or fiberglass hull, a ground/counterpoise system must be constructed. The counterpoise should have as much surface area as possible. About 9.5 square meters (100 square feet) should be provided for 2 MHz operation. A reasonably good ground can be achieved by bonding together large metal objects. Bonded to this ground should be two or three wide copper straps running as far as possible fore and aft, together with three or four cross members (ground plates may be effective on lower frequencies but are subject to fouling. Therefore, they are not recommended). Figure 2.10 shows a typical ground/counterpoise system.
2.5 POWER REQUIREMENTS
The transceiver is designed to operate directly fron 12 or 24 VDC negative ground vehicle electrical systems. Such systems use nominal 12 or 24 VDC batteries, but because they are normally being charged by an alternator or generator, average system voltage is higher. The actual voltage depends on system current draw and charging rate, but the average is taken to be 13.2 and 26.4 VDC with the transmitter operating.
The operating voltage of the transceiver is determined by the power amplifier (PA) assembly installed in the transceiver. Before connecting power, check the voltage tag on the end of the PA heatsink nearest the connectors.
The transceiver will accept NEGATIVE GROUND ONLY. Positive ground systems will require a inverter/ isolator. The transceiver has reverse polarity protection built in. If the unit does not operate, check the power supply connections.
2.5.1 CONNECTING THE MSR 6214 POWER SUPPLY
Connect the MSR 6214 AC Power Supply as follows: (P/N 697007-000-001, 12 VDC or PN 697007-000-002, 24 VDC).
a) Check the AC line voltage and DC
output voltage tags on the side of the MSR 6214 for correct input and output voltage settings. If voltages marked on tags do not meet application, refer to Sections 2.5.1.1 and 2.5.2.2.
b) Connect the MSR 6214 to the MSR 8000D using the power cable included with the power supply (P/N 600870-540-001). Cable connects between Jl of the power supply and connector J29 on the transceiver rear panel,
2.5.1.1 Line Voltage Setting
a) Disconnect power supply from AC line. Wait at least 3 minutes to allow hazardous DC voltages to bleed down.
b) Remove AC line voltage side of power supply.
c) Set both switches (under tag) to tag on appropriate position.
d) Replace AC line voltage tag with correct line voltage marking to outside.
2.5.1.2 Output Voltage Setting
a) Disconnect power supply from AC line. Wait at least 3 minutes to allow hazardous DC voltages to bleed down.
b) Remove power supply top cover.
c) Disconnect and remove control board.
d) Connect junpers on TB1 to appropriate locations:
12V - Jumper TB1-1 to TB1-2 and TB1-3 to TB1-4
24V - Stack junpers together, jumper TB1-2 to TB-3
NOTE
Jumper locations marked on top of TB1.
e) Reinstall control board, ensuring connection of transformer board pins on botton of control board and ribbon cable on side.
f) Locate jumper JP1 on control board and set jumper to appropriate position (see Figure 2.11 below, also marked on board).
g) Replace top cover.
h) Ensure that output voltage tag shows correct voltage - 12V is on one side of tag, 24 VDC is on other side.
2.5.2 CUSTOMER SUPPLIED POWER SUPPLIES
If the transceiver is used with other power supplies, use the DC power cord supplied with the transceiver (P/N 600452-540). This DC cable is supplied with approximately 15 feet of connecting cable. If the installation permits, the cable should be trimmed to a minimum length consistent with a neat installation. This will assure a minimum of voltage drop in the cable, under the high input currents present in transmit, particularly the 13 volt model. Connect the power lead marked "+" to the positive terminal of the power supply, and the lead marked "_" to the negative terminal of the power supply. If the power supply voltage output is adjustable, set the voltage to +13.2 VDC for the 12 VDC model transceiver, or +26.4 VDC for the +24 VDC model. The current capability of the power supply should be 30 amps for the 12 volt model, and 20 amps for the 24 volt model. A schematic of the transceiver power input connector is shown in Figure 2.12.
2.6 ANTENNAS AND GROUND SYSTEMS
CAUTION
The antenna radiates DANGEROUS RF VOLTAGE which can cause BURNS and INJURY. Do not touch the coupler antenna terminal, long wire or whip antenna while transmitting.
The transceiver is designed to drive a 50 ohm resistive antenna system with a 2:1 VSWR maximum. When used with the companion coupler, the system will drive the following antennas:
a) Whip, 3 meter (9 feet) - 1.6 – 30 MHz (vehicular mount)
b) Whip, 5 - 12 meter (16 - 35 feet) 1.6 - 30 MHZ
c) Longwire, 15 - 49 meter (50 - 150feet) - 1.6 - 30 MHz
Some general antenna system guide lines are:
a) Mount the antenna as high as possible.
b) Where possible, use antennas over 1/8 wavelength long at the lowest operating frequency. Short antennas are not efficient radiators.
c) Short antennas are most sensitive to ground loss. When a short antenna is used, the best possible ground systen should be obtained (see Figures 2.1 and 2.2).
d) on ships with non-metalic hulls, make the ground/counterpoise system cover as large an area as possible. Make maximum use of large metal objects, copper screen, the propellor shaft and properly bonded copper straps.
e) Use the lowest possible inductance ground connections for the transceiver and coupler.
2.7 ANTENNA COUPLER CONNECTIONS
If the MSR 4020A Antenna Coupler is part of the station system, refer to Publication Number 600262-823-001 for installation details. Figure 2.9 shows typical system interconnections.
NOTE
If the MSR 4020A Antenna Coupler is not connected, accessory plug 1A3-P22 (supplied in the transceiver accessory kit) must be installed on the accessory connector, 1A3J22. Otherwise, the transceiver will not transmit. This accessory plug contains a jumper between pins C ("transmitinterlock") and pin G ("ground"). The absence of this jumper prevents the exciter from being keyed. The plug also contains a jumper between pins R and to provide a required termination.
2.8 PA FAN OPTION
The fan option (P/N 600062-700-001), is required for FSK (RITY) operation of the transceiver. The fan is installed on the rear panel, over the PA heat sink, utilizing the four (4) mounting screws that are used to secure the power amplifier module to the rear panel. Electrical connections to the fan are made via a wiring harness and plug to a mating connector on the rear panel. Once installed, the fan will operate automatically to maintain an acceptable heat sink temperature. See Section 6 for fan option installation instructions.
2.9 REMOTE CONTROL OPTION
Remote Control of the MSR 8000D Transceiver is possible when used in conjunction with the optional MSR 6400 full function Remote Control PN 699023-000-xxx. Electrical connections to the remote control ar made via a 17 conductor control cable connected from the MSR 8000D rear panel audio connector 1A3J21, to J7 of the remote control.
NOTE
The transceiver rear panel connector board switch must be in the "REMOTE" position when the remote control unit is used, and in the "LOCAL" position when a remote is not connected. Refer to Fig.5.54 for switch location. Failure to have this switch in the proper position can prevent external keying of the transceiver from the audio connector and prevent ON-OFF power control in remote operation.
The MSR 8000D must be configured for remote operation with a factoryinstalled Remote Option P/N 600219700-001. Refer to Section 6 for details.
SECTION 3
OPERATION
3.1 GENERAL
This section describes the control and connector functions and gives canplete operating instructions for the transceiver.
3.2 FRONT PANEL CONTROLS AND CONNECTORS
Refer to Figure 3.1 for control locations.
3.2.1 VOLUME/POWER
Controls the received signal level at the speaker and PHONES jack. Click-off CCW position turns off transceiver primary power. VOLUME setting does not affect 600 ohm receive audio output.
3.2.2 SPEAKER SWITCH
Turns the internal speaker on and off.
3.2.3 CHANNEL/FREQUENCY SWITCH
Selects the active memory channel (one of ten) or selects the variable frequency mode. In switch positions 1 through 10, the transceiver operates at the frequency and mode stored in that memory channel (the MODE and FREQUENCY SELECT switches are disabled). In FREQ position, the transceiver will operate at the frequency and mode selected at the front panel. Simplex operation only is possible in this position.
3.2.4 MODE
Sets the transceiver operating mode. This control is not active during channelized operation (MODE is recalled from memory during channelized operation).
3.2.5 SQUELCH/NOISE BLANKER
Rotary action sets the squelch threshold. The squelch is defeated in fully CCW position (maximum threshold is fully CW): Pulling out the control turns on the noise blanker.
3.2.6 CLARIFIER CONTROL
Pulling out this control activates the clarifier (the amber lamp beside the knob lights to indicate clarifier ON). Rotating the control shifts the receive frequency at least +250 Hz froin the frequency indicated on the display. The clarifier does not affect the transinitted frequency. Frequency may be varied + 200 Hz when the MSR 6400 Remote Option is installed.
3.2.7 TUNE BUTION
Pushing this button initiates an antenna coupler tune cycle, if a coupler is connected. The coupler needs to be retuned after changing transmit frequencies.
3.2.8 PA/COUPLER STATUS LAMPS
These three lamps, FAULT, NOT TUNED and READY tell the operator the tune status of the coupler and the status of the PA. When the companion antenna coupler is used with the transceiver as a system, the lamps will indicate one of the conditions listed in Table 3.1.
When the companion coupler is not used and the transceiver is operating into a 50 ohm antenna, the lamps will indicate the conditions listed in Table 3.2.
3.2.9 DIMMER
Adjusts the brightness of the display and indicators for comfortable viewing in high or low ambient light.
3.2.10 SIGNAL/POWER METER
Indicates received signal strength relative to luv, and when transmitting, relative forward or reflected power.
3.2.11 FORWARD/REFLECTED POWER SWITCH
Determines whether the meter displays forward or reflected transmitted power. The reflected power reading should be very small (less than 0.l on the scale). A high reflected power reading indicates an antenna mismatch.
3.2.12 KEY LIGHT
This red LED in the upper right corner of the meter scale lights when the transmitter is keyed. If the light does not light when the microphone is keyed, the transceiver may have an internal fault which inhibits the transmitter.
3.2.13 MODE DISPLAY
Shows a letter corresponding to the tranceiver mode. A = AME, C = CW, U = USB, L = LSB and F = FSK and 1l = A3A.
3.2.14 CHANNEL NUMBER DISPLAY
Shows the number of the memory channel selected. When the CHAN/FREQ knob is in FREQ position this display is blank.
3.2.15 FREQUENCY DISPLAY
Shows the transceiver operating frequency.
3.2.16 FREQUENCY SELECT SWITCHES
Permit the selection of the transceiver operating frequency. They are active only in FREQ position of the CHAN/FREQ switch or in LOAD MEMORY mode. The switches affect the digit directly above them and the two least significant digits carry into the third. Frequencies above 29.9999 MHz or below 1.6000 MHz cannot be selected.
3.2.17 LOAD/OPERATE
This switch controls memory loading. In the OPERATE position, the transceiver operates normally. In the LOAD MEMORY position, the receiver audio is muted, transiission is inhibited and the memory may be loaded. A warning LED lights when in the LOAD MEMORY position.
3.2.18 LOAD RX BUTTON
Is only active in the LOAD MEMORY switch position. Pushing the button loads the receive frequency and mode into a selected channel.
3.2.19 LOAD/CHECK TX BUTTON
In the OPERATE position, pushing the button displays the transmit frequency stored in a selected memory channel. In LOAD MEMORY position, pushing the button loads the transmit frequency and mode into a selected memory channel.
3.2.20 MIC CONNECTOR
Connector for dynamic microphone, carbon microphone, handset or CW key.
3.2.21 AUX CONNECTOR
Connector is wired in parallel with MIC Connector and may be used with the same accessories.
3.3 REAR PANEL CONTROLS AND CONNECTORS
Refer to Figure 3.2 for locations.
3.3.1 POWER CONNECTOR
Is used to connect DC power to the transceiver. Also contains connections to a remote power relay in the optional AC power supplies. Mates with the standard MS connector MS3106A 24-lls (supplied).
3.3.2 ACCESSORY CONNECTOR
Connects accessory equipment such as the companion antenna coupler. Mates with the standard MS connector MS3106A 28-21P (supplied).
3.3.3 AUDIO CONNECTOR
Connects to/from 600 ohm balanced audio lines or connections to audio remote unit. Mates with the standard MS connector MS3106A 20-29P (supplied).
3.3.4 ANTENNA CONNECTOR
Connects the RF input/output of the transceiver. Mates with the standard PL-259 connector (supplied).
3.3.5 PA FAN CONNECTOR
Supplies DC power to optional PA fan kit.
3.3.6 GROUND STUD
Used for making a good RF ground to the transceiver.
3.3.7 RECEIVER/EXCITER FUSE
Protects the receiver and exciter portions of transceiver.
3.3.8 PA FUSE
Protects the RF power amplifier module.
3.4 OPERATOR INTERNAL CONTROLS
The transceiver is equipped with several internal controls as a convenience which the operator may wish to adjust. They are: function enable/disable switch, CW delay adjust, 600 ohm remote transmit audio input adjust and the 600 ohm receive audio output level adjust. See Figure 3.3 for the location of these controls.
3.4.1 FUNCTION ENABLE/DISABLE SWITCH
This switch (lAlA9-Sl) consists of eight (8) co-located switches in one housing. Each section of the switch controls a different function. They are as follows (from right to left):
3.4.1.1 Memory Program Enable SW-l
To be able to program the transceiver memory, this switch must be ON. It may be switched off to prevent inadvertent reprogramming of the memory.
3.4.1.2 Manual Frequency Enable SW-2
NOTE
This switch functions only if wire jumper Wl on the logic board (Figure 5.31) is removed. Units are shipped with this jumper installed, unless specified by customer order.
With the jumper renoved, and switch S1-2 set to "OFF", the transceiver frequency and mode cannot be changed when the CHAN/FREQ switch is in the "FREQ" position. Setting the switch to "OFF" will freeze the frequency and mode to those last selected, except that the mode may change to A3A when the switch is thrown.
3.4.1.3 Tuning Beep Tone SW-3
The transceiver generates a beep tone in the speaker when the companion coupler is in the process of tuning. The volune of the tone may be regulated by the VOLUME control. The tone may be disabled by turning its switch OFF.
3.4.1.4 Surveillance Tune SW-4
The companion coupler contains the capability to continuously monitor the state of tune of the antenna over a sinall range and retune automatically when the VSWR exceeds 2:1. However, RF power must be present for this feature to work, so surveillance tune works best in AME or FSK modes where continuous carrier is present.
If a frequency or antenna VSWR change is made which is out of the surveillance tune range, the FAULT indicator will flash,
Surveillance tune is activated by turning the switch to ON position.
3.4.1.5 Auto-Tune SW-5
When enabled, the companion coupler will tune when a channel change or frequency change greater than 10 kHz is made in the transceiver. Tuning does not commence until the transceiver is keyed.
3.4.1.6 VSWR Retune SW-5
When this switch is closed a coupler tune will be initiated whenever the antenna coupler VSWR is greater than 2:1. When the companion linear amplifier is used, a coupler tune cycle will be initiated if amplifier or antenna coupler VSWR exceeds 2:1. (This feature is not available with the MSR 4020 Antenna Coupler.)
3.4.1.7 Switches 7 and 8
Spare switches not currently used.
3.4.2 CW DELAY ADJUST
This control (1A1A9-R8) adjusts the time delay between transmitting and receiving, when the transceiver is operated in the CW mode.
3.4.3 600 OHM REMOTE TRANSMIT AUDIO INPUT
This control (IA1A3-Rl) adjusts the level of 600 ohm transmit audio that is applied to the transceiver from remote sources or optional equipment. Nominal audio input is 0 dBm.
3.4.4 600 OHM RECEIVE OUTPUT LEVEL
This control (1A1A7-R54) adjusts the level of 600 ohm receiver audio that can be supplied from the transceiver to remote sources or optional equipment. Nominal output is 0 dBm, adjustable to +10 dBm.
3.5 TRANSCEIVER OPERATION
3.5.1 OPERATING THE TRANSCEIVER WITH 50 OHM ANTENNA OR 50 OHM LOAD
a) Connect the transceiver to the proper DC power source.
Check the voltage tag on the PA heatsink, Connect a 50 ohm antenna or a 50 ohm, 125W dummy load to the antenna connector.
NOTE
When the automatic antenna coupler is not used, the accessory plug, 1A3P22, which jumpers pin C (key interlock) to pin G (ground), must be installed in 1A3J22. The key interlock line (pin c) must be grounded for the transceiver to transmit.
b) Connect the microphone. Turn power switch to ON and advance VOLUME control to half rotation.
c) Put CHAN/FREQ control in FREQ position.
d) Set MODE switch to desired node.
e) Turn SQUELCH control fully ccw.
f) Check that CLARIFIER control is pushed in.
g) Adjust DIM control to comfortable viewing level.
h) Use FREQUENCY SELECT switches to select desired operating frequency,
i) Set SPEAKER switch to ON.
j) The unit should now receive. The volume may be adjusted to a comfortable level.
k) The SQUELCH control may now be turned slowly clockwise to a position where background noise is squelched during periods when no signal is present. This is the point of minimum squelch thres hold, and further clockwise adjustment beyond this point will require a stronger received signal to cause an audio output.
ㅣ) 'To transmit, press the microphone button and speak at a normal level with the microphone held 12 to 50 m from the mouth (1/2 - 2 inches). The transceiver has an audio compressor which adjusts the transmit level automatically.
3.5.2 LOADING TRANSCEIVER MEMORY
a) Place the OPERATE/LOAD MEMORY posiswitch in the LOAD MEMORY position. See that the LOAD MEMORY LED lights. If it does not, the PROGRAM ENABLE Switch is off. Remove the top cover and switch PROGRAM ENABLE ON (See Figure 3.3).
NOTE
Before the memory is programmed for the first time, or if the battery has been removed from the logic board, the display may indicate 29.9999 MHz USB. This is the "DEFAULT" frequency and mode that is in the operating system prom to prevent invalid frequency or mode data from being displayed or transmitted.
c) Select the desired channel number with the CHAN/FREQ switch. Channels may be loaded in any séquence.
d) Select the desired mode with the MODE switch.
e) Select the desired frequency with the FREQUENCY SELECT switches.
NOTE
If different receive and transinit frequencies are to be loaded for half Cuplex operation, select the receive frequency first.
f) When loading a simplex frequency (same TX and RX frequency), push the Rx button then the CHECK/TX button. (Do not push the buttons at the same time.)
NOTE
If the companion 1 kW amplifier and antenna coupler are connected, the antenna coup ler power should be turned off prior to loading transmit frequencies. The CHECK/TX button has dual functions; in addition to loading frequency information, it also activates the silent tune feature of the MSR 4030 coupe ler. Refer to 3.5.6 for silent tune operation.
g) When loading the receive frequency of a half-duplex pair, push only the RX button.
h) To load the transmit frequency of the half duplex pair, select the transmit frequency, then push the CHECK/TX button,
NOTE
When loading different transmit and receive frequencies, as soon as the CHECK/TX button is released, the display will switch to the receive frequency. DO NOT press the CHECK/TX button again, as this will then load the receive frequency into the transmit memory. TO check the transmit frequency, place the OPERATE/LOAD MEMORY switch in the OPERATE position, then push the CHECK/TX button. The transmit frequency will be displayed as long as the button is held.
i) Select a new channel with the CHAN/FREQ switch. Repeat steps c through g.
j) When all channels have been pro grammed, return OPERATE/LOAD MEMORY switch to OPERATE position. The unit is now ready for operation. Refer to Table 3.3 for a summary of load memory procedure.
3.5.3 PERATING THE TRANSCEIVER WITH THE COMPANION COUPLER
a) Connect the transceiver to the proper DC power source. Check the voltage tag on the PA heatsink. Connect the control cable from the companion coupler to the transceiver accessory connector. Connect a coaxial cable from the companion coupler RF input to the transceiver's antenna connector.
b) Connect the antenna to the ceramic antenna post on the antenna coupler. See Sections 2.4 and 2.6.
c) Turn the power switch to On.
d) Select the operating channel or the desired frequency and mode.
e) Note that the FAULT LED shows a steady indication.
f) Push the TUNE button. The FAULT LED will extinguish and the NOT TUNED LED will light. Note that the receive audio is muted during the tune cycle.
g) If the TUNING BEEP TONE switch is on (see Figure 3.3), note that the volume of the beep can be set with the VOLUME control.
h) When the companion coupler completes tuning, the NOT TUNED light will extinguish and the READY LED will light. The system is now ready for operaiton.
i) If the coupler cannot tune the antenna within 30 seconds, (because of a damaged antenna or a broken cable, for example), the FAULT indication will flash. The operator may start another tune cycle by pushing the TUNE button. If successive tune cycles produce a flashing FAULT indicator, the operator should attempt to find the cause of the problem before proceeding.
3.5.4 OPERATING THE TRANSCEIVER WITH THE COMPANION 1KW AMPLIFIER
1. Refer to Paragraph 3.4 "Amplifier Operation" in the Linear Amplifier Operation and Maintenance Manual, Publication No. 600241-823-001.
3.5.5 OPERATING THE TRANSCEIVER WITH THE COMPANION 1KW AMPLIFIER AND 1KW AUTOMATIC ANTENNA COUPLER
1. Refer to Paragraph 3.4.2 in the Linear Amplifier Operation and Maintenance Manual, Publication No. 600241--823-001, and Paragraph 3.2 in the 1KW Antenna Coupler Manual, Publication No. 600236-823-001.
3.5.6 SILENT TUNE MODE
When using with the 1KW Amplifier and Antenna Coupler in the silent tune mode, ten channels can be programmed on the "CHANNEL/FREQ" knob on the front panel of the transceiver. Everytime the antenna coupler is tuned in one of the ten channels, the tuning information is stored in memory within the coupler for that particular channel. To use the silent tune mode, pick a channel that has already been tuned and push the "CHECK TX" pushbutton which is located on the front panel. The coupler will automatically position the tuning elements from memory and the "READY" LED will come on. Because no RF carrier is used, the "TX" LED on the meter will not light and there will be no forward power during the tuning sequence in the silent tune mode. However, there may be a reflected power indication on the meter during tuning due to logic voltages.
3.6 MICROPHONE SELECTION AND AUDIO INPUT LEVELS
The MSR 8000D is configured for use with most microphone types. The handheld microphone (P/N 600352713-001) is supplied with the radio. The H-250/U Handset (P/N 600002386-001) is optional.
Carbon microphones such as the H-33 can also be used, but a configuration jumper located on the Transmit Modulator board, 1A1A3, must be moved. If microphones with more or less output than those specified or supplied by ITT are used, R-96 on the Transmit Modulator board can be adjusted for more or less gain (see Section 5.9).
For certain types of digital encoding equipment, audio compressors can create distortion. Jumper plug JP-2 on the Transmit Modulator board can be used to disable the compressor. If JP-2 is connected 1 to 2, the compressor will be disabled and the input audio level will have to be adjusted to produce 0.23-0.27 VPP at 1A1A3-TP1.
SECTION 4
FUNCTIONAL DESCRIPTIONS
4.1 GENERAL
The transceiver is a modularized state of the art HF conununications transceiver. The information contained in this section describes the major functions of the transceiver. The discussions of the functional descriptions of the transceiver will be presented in sixteen parts. Each part will contain a discussion of the major functional elements of that part. For a detailed circuit description of a particular part, refer to Section 5 of this manual,
Figure 4.1 shows an overall block diagram of the transceiver. Refer to this diagram as the function of each section is described.
4.2 HALF OCTAVE FILTER BOARD, 1A1A2
This assembly performs part of the receive mode preselector function, and in the transmit mode, filters the output of the power amplifier. Located on this board are eight (8) elliptical low pass filters with cutoff frequencies of 2, 3, 4, 6, 9, 13, 20 and 30 MHz. Also located on this board are the VSWR detector, ALC detector and amplifier, ACC detector and amplifier and via feedback from the power amplifier assembly, 1A3A1, circuits that will protect the solid state PA from conditions of VSWR, over current, over voltage and over temperature.
The desired elliptical filter is selected automatically by relay control ground signals from the logic board, 1A1A9. In the transmit mode, these filters reduce the harmonic output to better than -50 dB. In the receive mode, these same filters attenuate signals that are above that of the desired band of operation.
4.3 125 WATT POWER AMPLIFIER ASSEMBLY, 1A3A1
The all solid state power amplifier accepts the +13 dBm RF drive input from the mixer assembly, 1A1A5, and provides a nominal 38 dB gain to produce 125 watts output to the antenna (through the low pass filters) in the transmit mode. Receive/transmit signal paths are controlled by relay Kl, to route the antenna input directly to the high pass filter, lAlA4, in the receive mode.
Also contained on this board are circuits that sense PA over voltage, over current and over temperature. These voltages are fed to the half octave filter board, lAlA2, which via feedback to the transmit modulator board, 1A1A3, controls overall transmitter gain and power output.
4.4 HIGH PASS FILTER BOARD, 1A1A4
This assembly performs part of the receive mode preselection and receive RF amplification. In the transmit mode, the output of the mixer board, 1A1A5, is filtered by this board. Contained on this assembly are eight (8) elliptical high pass filters with cutoff frequencies of 1.6, 2, 3, 4, 6, 9, 13, and 20 MHz.
The desired filter is selected automatically by ground signals from the logic board, 1A1A9, This board also contains a broadcast filter which provides attenuation of greater than 70 dB to broadcast signals (signals below 1.6 MHz), and a very low noise receive RF amplifier. A transmit/ receive relay is used to bypass the broadcast filter and RF amplifier in the transmit mode.
Additional circuitry located on this board provides analog voltages which are supplied to the transmit modulator board, lAlA3, to more accurately establish the A3A carrier level on transmit.
4.5 HIGH LEVEL MIXER BOARD, 1A1A5
4.5.1 GENERAL
The High Level Mixer Board (Figure 5.23) is interchangeable with the Mixer Board, P/N 601075-536, previously used in the MSR 8000, MSR 5050, and MSR 6700. In RECEIVE mode, it converts a 0 to 30 MHz RF input to a lst IF of 59.53 MHz and subsequently a 2nd IF of 5 MHz. In TRANSMIT mode, it converts a 5 MHZ input to 59.53 MHz and then to RF outputs of 1.6 to 30 MHz, All circuit interfaces are at 50 ohm impedance levels.
Figure 4.1 is a functional block diagram of the board. In RECEIVE mode, inputs on the RX input are selected by the RF switch and filtered by the 30 MHz LP filter. The 1st mixer, with an amplified LO input of +21 dBm, 50.53 MHz to 89.53 MHz, converts the RF signals to a 59.53 MHz IF. The mixer is provided a broadband IF termination by a lossless constant resistance network and a non-reflective crystal filter network. A bilateral amplifier provides 18 dB gain which is controllable by a delayed AGC input of 0 to 9 volts. A second crystal filter at 59.53 MHz controls spurious responses due to the second mixer and complements the selectivity of the first filter and the system information filter for a total 120 dB ultimate selectivity. The second mixer, with an amplified LO of +10 dBm, converts the 59.53 MHz signals to a 5 MHZ IF. The second Lo amplifier may be gated off by 9 volt pulses to accomplish noise blanking.
In transmit the signal path is reversed with inputs at the 5 MHZ IF converted to a 59.53 MHz IF, and amplified by the reversed bilateral amplifier. The RF switch directs the 1.6 to 30 MHz outputs from the Ist mixer to the TX amplifier to produce outputs to +15 dBm.
4.5.2 DETAILED DESCRIPTION
4.5.2.1 RX Control
With a TIL low at pins 15 and 16, Q8 saturates putting +9V on all RX functions.
4.5.2.2 RF Switch
CR1 is biased to conduction by the current through R1 with L1 and L2 providing a high impedance to the signal pth for RF signals. The resulting voltage across Rl biases CR2 off, isolating transmit circuits from the signal path. The input signals are thus conducted through C1, CR1, and C3 to the low pass filter.
4.5.2.3 Low Pass Filter
The low pass filter is a 7-element elliptical design (C4 through C8, L3 and L4) with a cut off frequency of 31 MHz. This filter attenuates outof-band spurious signals in both receive and transmit.
4.5.2.4 First Mixer
Signals from the Low Pass Filter are applied to pin 1 of the first mixer, MX1, a high level double-balanced diode mixer. These signals (0-30 MHz) are modulted with +21 dBm LO signals (59.53 to 89.53 MHz) applied to pin 8 to produce a first IF of 59.53 MHz at pins 3 and 4.
4.5.2.5 Constant Resistance Network
The Constant Resistance Network provides a 50 ohm load to signals from the mixer at frequencies much greater than the IF frequency R17 provides the 50 ohm load at high frequencies when C30 is short, and at low frequencies when L14 is short. C29 and L1 are series resonant at 59.53 MHz to couple the signal to the 90° hybrid network, maintaining a 50 ohm load at frequencies near the 59.53 MHZ IF.
4.5.2.6 90° Hybrid/Filter Network
This circuit maintains a 50 ohm impedance by phasing equal mismatches from the two identical crystal filters FL1 and FL2 so that they cancel at the circuit input and add across R18 at an isolated port. T3 witn C31 and C32 form a quadrature hybrid tuned broadly to 59.53 MHz at a 50 ohm impedance. This circuit splits inputs from L13 to equal outputs at L15 and L16 phased 90° apart. L15 and C33 match the 2.3k ohm filter impedance of FL1, L16 and C34 perform the same function for FL2. Matching back down to 50 ohms is accomplished by L19, C35 and L20, and C36. L17 and L18 are used to tune the residual capacitance across the filters to increase the ultimate rejection. A second 90° hybrid (T4, C37 and C38) adds the signals from each filter. The total loss through the whole hybrid/filter network is typically 3.5 dBm.
4.5.2.7 Bilateral Amplifier
The Bilateral Amplifier consists of receive (Q9) and transmit (Q10) amplifiers activated by a 9 volt RX or 9 volt TX control signal. These amplifiers switched into the signal path by CR5, CR9 or CRI0, and CR7, allow reverse signal flow in transmit applications since all other circuits are inherently bilateral.
The amplifiers are feedback controlled to maintain a 50 ohin input/ output impedance with gain controlled by feedback resistor impedances and the relatively low broadband collector output impedance of ance of 600 ohms.
In Receive, the signal flows through C38, CR5 (biased by R21 and R22 with R21 also serving as a feedback resistor. The gain is set to 18 dB by the ratio of the collector load of 600 ohms and the emitter resistor R23. L25 and C45 match the 600 ohm output to 50 ohms with the output routed through pin diode CR9. The bias through switches CR5 and CR9 produces an 8 volt drop across L21, R20 at the input and L30, R30 at the output which reverse biases transmit output which reversehes CR7 and path pin diode switches CR7 and CR10. The maximum signal level for strong signals is limited by a delayed AGC (DAGC) signal from pins 39 and 40. The DAGC input (0 to 9 volts) biases shunt pin diodes CR4 and CR8 which attenuate the signal at 09 input and output for a total of 40 dB at 0 volts DAGC. Bias current is limited by resistors R31 and R29. CRll delays the output attenuation for optimum linearity. The DAGC circuit is necessary to maintain inband intermodulation rejection of 30 dB at high input signals. The DAGC attenuation varies from 1 dB at 8.3 volts to 40 dB at 0 volts.
in transmit, the circuit of Q10 is connected through CR7, CRI0 by the bias produced through L24, L29 by the 9 volt TX signal, The circuit is identical to that of Q9 except for the values of R26 and R28 which produce a 16 dB gain.
4.5.2.8 Crystal Filter
A second crystal filter, F13 at 59.53 MHz is required to reject spurious responses due to the second conversion especially the second IF image at 49.53 MHz. This filter, identical to FL1 and FL2, is matched to 50 ohms input and output by L31, L33 and C55, C56 with ultimate rejection improved by L32.
4.5.2.9 Second Mixer and 5 MHz Filter
The 59.53 first IF signal is converted to a second IF of 5 MHz by a second double-balanced diode mixer, MX2. The 5 MHz output signal is filtered by a 5 MHz low pass filter C62, C63, L36 to reject the 59.53 MHZ IF feed through, the 54.53 MHz second LO, and other undesired mixer outputs.
4.5.2.10 First LO Amplifier
The first LO amplifier produces a +21 dBm signal at Mxl (pin 8), from 0 dBm board inputs from 59.53 to 89.53 MHz at pin 3. Q5 and Q6 are common gate FET's paralleled for a 50 ohm broadband input with a transconductance to produce a 6 dB gain into the 50 ohm load produced by T2. The FET's are self-biased to 10 mA by R16. L8, L9, and C20 form a 40 MHz high pass filter to reduce low frequency Lo noise.
Q4 is a grounded emitter amplifier with 15 dB gain which produces the +21 dBm LO signal required by Mxl. Q3 is a bias regulator which maintains the voltage drop across R14 (due to the current of Q4) constant by controlling the base current of Q4 through R15. L12 and C28 broadly tune the output for a relatively flat response from 59.53 to 89.53 MHz. Biased at 100 mA, the amplifier can produce a linear output of 250 milliwatts.
4.5.2.11 Second Lo Amplifier
Q11 and Q12 are paralleled JFET's which produce a +10 dBm output at MX2, pin 8 from a 0 dBm, 54.53 MHz second LO input at board pin 41. The FET's are self-biased by R32 to 10 milliamperes. L35 and c12 match the 50 ohm level of MX2 to 1.2k ohms at the FET drain to produce a 10 dB gain. With a 9 volt input at board pin 37, Q13 produces an 8 volt bias across R32 which cuts the LO amplifier off, (cutoff voltage of Qll, 012 is 6.5 volts maximum) which in turn cuts the mixer off and thus breaks the signal path. This is used as a noise blanker gate in the MSR 8000D and may be used as a transmit inhibit gate in transmit applications.
4.5.2.12 Transmit Amplifier
Q1 and Q2 are feedback controlled amplifiers which increase the level of signals from the first mixer, Mxl to +17 dBm outputs, 1.6 to 30 MHz at board pin 6. Signals from the mixer, MXl are routed through the low pass filter (C4-C8, etc.) C3, CR2, C14, and C15 to the base of Q2. Q2 is biased for 2.9 volts at the base by R9, R10, and R11. R7 and R8 produce 30 milliamperes bias current, with R7 setting the gain and R9 controlling the input/output impedance of 50 ohms. C18 as well as L7 compensate the high frequency roll off. Q1 is the identical circuit with values changed to produce a capability of 160 milliwatts linear output. In addition, the base bias is altered to add CR3
4.6 IF FILTER BOARD, 1A1A6
The IF Filter board contains the three 5 MHz information filters and amplifiers (bilateral) used in both transmit and receive modes. These filters are: FL1 -lower sideband, FL2 -upper sideband, and FL3 -AM. The appropriate filter is selected by diode switching via mode information from the logic board, 1A1A9. During the receive mode, the 5 MHZ IF signal from the mixer board, 1A1A5, is passed through the appropriate IF filter and further amplified in three stages. The gain of the IF output is adjustable. An AGC voltage is applied from the audio squelch board, 1A1A7, to two of the If amplifier stages to reduce the IF gain on very strong received signals.
During the transmit mode, a double sideband signal from the transmit modulator board, 1A1A3, is applied. The appropriate filter will remove the unwanted sideband of the transmitted signal. The signal is then amplified and applied to the mixer board, 1A1A5.
Other circuits on this board include an amplifier combiner, U3A, which applies carrier for AME operation, and DC switches Q1 and 02 which apply voltages to the appropriate transmit or recieve amplifier stage.
4.7 AUDIO/SQUELCH BOARD, 1A1A7
The audio/squelch board is used in the receive mode only. This board accepts the 5 MHz IF output from the TF filter board, 1A1A6, and performs the final detection function to convert the intermediate frequency signal into usable intelligence in the audio frequency range. This process involves two discrete, but not simultaneous, detector functions. A product detector is used in all modes except the AME mode. In the AME mode an envelope detector is used.
Two separate audio outputs are provided. A 600 ohm line audio output is applied to the rear panel connector, 1A3J24, and a low level output is applied to the speaker/driver board, 1A1A8, to provide the front panel speaker and headphones/handset audio.
Located on this board are an input IF amplifier, AGC detector and amplifier, AM/product detector, squelch amplifiers and gating circuitry. In the AME mode, AGC is carrier derived, in CW, SSB and FSK modes, AGC is derived from the detected audio. Fast attack fast decay is uded for AME and FSK signals, and fast attack slow decay is used for sideband and CW signals. AGC voltage to the IF filter board, LALA6, and delayed AGC voltage to the mixer board, 1A1A5, controls the receiver gain.
Other circuitry and functions, through this board, are side tone and mute functions. The rear panel audio (600 ohm) is unaffected by operation of the squelch control.
4.8 SPEAKER/DRIVER BOARD, 1A1A8
The speaker/driver board contains the four watt speaker amplifier, DC volume control circuit, tuning beep generator and channel number buffers.
Audio from the audio squelch board, 1A1A7, is applied to this board through an opto-coupler. The resistance of this opto-coupler and thus the output of the speaker/driver, U3 is a function of the setting of the volume control located on the front panel, 1A2.
As the volume control is supplyiny a variable DC voltage only, hum and noise rejection of the audio amplifier is exceptionally good.
The audio output from this board drives the front panel speaker, LA2LSI, the headphone jack, 1A2-J32, and the audio output pin of the microphone jack, 1A2-J34.
The beep tone, when enabled by the function ENABLE/DISABLE switch, 1A1A9-S1-3, causes a dual timer, U2, to generate 2 kHz "beeps", as the rernote antenna coupler is operated. The amplitude of the beeps can be adjusted by the volume control.
The channel number buffers located on the board buffer the BCD channel number information from the logic board, lAlA9, before it is routed to the rear panel accessory connector 1A3-J25.
4.9 TRANSMIT MODULATOR BOARD, 1A1A3
The transmit modulator board contains the speech compressor, balanced modulator, AME carrier insertion circuit, ALC amplifier and control, CW tone gate and 5 MHZ double sideband amplifier.
Audio inputs from the front panel (carbon or dynamic microphone) and the 600 ohm audio input from the rear panel, are translated into a 5 MHz double sideband signal and then applied to the IF filter board, LALA6. Transmit ALC and ACC voltages are applied to this board for the establishment of the transmitter gain, ALC controls the output in CW, FSK and SSB, whereas, ACC controls the carrier level in AME mode. All transmit audio passes through an audio compressor which maintains a high average level of output. This ultimately results in a higher average level of RF output power from the transceiver. In addition, no microphone level adjust control is required. An adjustinent, 1A1A3R1, is provided on the board to reduce the 600 ohm audio input level, if necessary, when audio levels from accessory or optional equipment exceeds the recomnended 0 dBm audio input level.
The CW tone gate, 03, is an electronic switch which, in the CW mode, supplies a 1 kHz signal (supplied by the reference board, 1A1A12) to the balanced nodulator, 02. This signal becomes the CW carrier, and is applied as the CW key is closed. A portion of the 1 kHz tone is applied to the audio/squeich board, 1A1A7, for sidetone.
4.10 LOGIC BOARD, 1A1A9
The logic board contains the microprocessor and supporting circuitry and supplies frequency, band, mode and channel information to other assemblies and/or optional equipment. This board receives input data from the front panel and/or rear panel accessory connector. This data is processed by the microprocessor, and then appropriate commands are applied to other boards in the radio for operation. In addition, ten channels of meinory can be stored by U4. A low leakage lithium battery maintains memory xwer when operating power is not applied or is removed from the transceiver.
Also located on this board is the program ENABLE/DISABLE Switch, si. This eight section switch allows memory, beep tone, manual control mode of the transceiver and surveillance tune mode of the automatic antenna coupler to be enabled or inhibited.
4.11 FREQUENCY SYNTHESIZER, 1A1A12, 1A1A13, 1A1A14, 1A1A15
The frequency Synthesizer consists of four subassemblies: reference board, 1A1A12, the minor loop board, 1A1A13, the translator loop board, 1A1A14 and the major loop board, 1A1A15. The synthesizer generates the three local oscillator signals that determine the operating frequency of the transceiver. These signals are obtained from the 5 MHz reference oscillator directly, by a combination of direct synthesis and digital phase lock techniques. Frequency accuracy is dependent only upon the 5 MHz CXO oscillator on the reference board.
4.11.1 REFERENCE BOARD, IA1A12
The reference board contains the 5 MHZ 1CXO, which determines the frequency accuracy of the transceiver.
The third L (5 MHz) is supplied by this board to the transmit modulator board, 1A1A3, to be used as a carrier generator on transmit, and to the audio/squelch board, 1A1A7, to be used as a product detector injection signal on receive. The 1 kHz is also supplied to the minor loop board, 1A1A13, as a phase detector reference. Other circuitry on this board includes a +24 VDC power supply and a 50 kHz reference signal, both are applied to the major loop board, 1A1A15.
4.11.2 MINOR LOOP BOARD, IA1A13
This assembly supplies the l-1.0999 MHz signal to the translator loop board, 1A1A14, that determines the 100 Hz, 1 kHz and 10 kHz digits of the transceiver frequency. Input to this board is a 1 kHz reference signal from the reference board,
1A1A12, and 100 Hz, 1 kHz and 10 kHz data information from the logic board, 1A1A9.
4.11.3 TRANSLATOR LOOP BOARD, lAlA14
The translator loop board provides the 54.53 MHz Second Lo, which is applied to the mixer board, 1A1A5. This signal originates from a crystal oscillator and is not referenced to the frequency standard, therefore a small frequency error can exist in the second L. Due to the inixing scheine used in this assenbly, the same error appears on the first LO frequency and is therefore cancelled at the output of the first nix board, lAlA5. This board supplies to the major loop board, 1A1A15, 55.53–55.6299 Myz signal. This signal is essentially a mixture of the low digit signal 1-1.0999 MHz, and the second LO (54.53 MHz including frequency error).
4.11.4 MAJOR LOOP BOARD, AA15
The major loop board supplies the first Lo signal (61.13-89,53 MHz) to the mixer board, 1A1A5. The first LO is a phase locked oscillator covering the frequency range of 61.1300 MHz to 89.5299 MHz, in 100 kHz steps. The exact frequency of the first LO is given by:
F1= 61.1300 + Fd + e (MHz)
where F1 = first to frequency
Fd = dialed frequency
e = second LO error
On receive, the first LO is used to convert the incoming signal up to the first IF frequency (59.53 MHz). On transmit, the first Lo is used to convert the transmit signal at the first IF frequency down to its final operating frequency.
This board determines the LO MHz, l MHz and 100 kHz digits of the transceiver frequency. Inputs to this board are the 55.53-55.6299 MHz signal from translator loop board, 1A1A14, a 50 kHz signal and +24 VDC fron the reference board, 1A1A12, and 10 MHz, 1 MHz and 100 kHz data information from the logic board, 1A1A9.
4.12 NOISE BLANKER, 1A1A1
The noise blanker is a high gain noise pulse amplifier and detector which is used to gate off the second LO that is applied to the mixer board, 1A1A5, thus effectively blanking the receiver during periods of interferring noise pulses such as ignition noise, etc. The input of the amplifier is tuned to 35 MHz (above the transceiver operating frequency). Impulse noise occupies a wide bandwidth and can effectively be amplified and detected at this frequency. Using this frequency prevents saturation of the noise blanker by large signals in the 1.4 to 30 MHz band. The noise blanker input is connected to the output (ANT) of the half octave filter board, lAlA2, and the output of the noise blanker is applied to the mixer board, 1A1A5.
4.13 POWER SUPPLY REGULATOR ASSEMBLY, 1A1A10
The power supply regulator assembly supplies two of the four regulated operating voltages for the transceiver. The two voltages provided by this assembly are +9 volts and +5 volts regulated DC. +12 or +24 VDC from the rear panel power connector, 1A3J30, is applied to the input. Ul, and transistors Ql and Q2 form a +5 volt high efficiency switching regulator. U2, and transistor Q3 form a + volt high efficiency regulator. The voltage output of the 5 and 9 volt regulators are adjustable.
The output of the 9 volt regulator is applied to the 1A1A2, 1A1A3, 1A1A4, 1A1A5, 1A1A6, 1A1A7, 1A1A8, 1A2 and 1A3 assemblies.
The output of the +5 volt regulator is applied to the 1A1A8, 1A1A9, 1A1A11, 1A1A12, 1A1A13, 1A1A14, 1A1A15 and 1A2 assemblies.
4.14 CHASSIS/MOTHER BOARD, 1A1A1A1
All subassemblies in the transceiver are electrically or mechanically connected to the chassis/mother board. The chassis houses all plugin PC boards and provides shielding. The mother board contains all interconnecting wiring in the transceiver. All plug-in PC boards connect to the mother board through PC edge connectors. Keys on the connectors discourage plugging PC boards in the wrong slots. The only components located on the inother board are inductors and bypass capacitors, with the exception of the receiver protector described in 4.14.1.
4.14.1 RECEIVER PROTECTOR (PART OF LALALAL)
The receiver protector consists of two pair of back-to-back connected reverse biased PIN diodes, referenced to +3 VDC and connected in parallel with the receiver input (receiver input to 1A1A4). Any RF voltages in excess of three volts peak will cause conduction of the PIN diodes, thereby protecting the receiver front end.
This type of circuit causes little, if any, received signal attenuation, and does not degrade the excellent receiver low IM distortion characteristics.
4.15 FRONT PANEL ASSEMBLY, 1A2
The front panel contains all switches and controls for transceiver operation. The microphone connector, 1A2J34, auxillary connector, 1A2J35, meter, speaker and antenna coupler tune initiate pushbutton switch are all located on the front panel. Part of the front panel assembly includes the front panel PC board assembly, 1A2A1, which contains the the frequency display and associated circuitry. The front panel is pluggable to the transceiver mother board via connectors 1A2A1-J28 and 1A2P17, and ribbon cable.
4.15.1 FRONT PANEL BOARD, 1A2A1
This board, which is part of the front panel assembly, contains the mode, channel, frequency display, display drives and decoders. This board is connected to the front panel via 1A2J27, and provides the display digit select signals to the front panel UP/DOWN toggle switches to generate the T0 and T1 commands used by the inicroprocessor on the logic board, lAlA9, to change the transceiver frequency Signals from the microprocessor are then applied to this board via 1A1A1A1-J18 for the correct display of channel, mode and frequency. Other circuitry on this board includes the dimmer control circuitry and logic gates, which in conjunction with the front panel switches, supply +5 VDC for operation of the mode switch.
4.16 REAR PANEL ASSEMBLY, 1A3
The rear panel assembly contains the power input, antenna, 600 ohm audio, and accessory connectors. The DC power contactor, power amplifier assembly, 1A3A1, and fuses are also located on the rear panel assembly. The rear panel is pluggable to the transceiver mother board via connectors P20, P24 and P25.
SECTION 5
MAINTENANCE
5.1 GENERAL
This section provides information for routine maintenance, repair and evaluation of the overall performance of the transceiver. Modular construction of the transceiver lends itself to a logical and straight forward troubleshootingting procedure. By referring to the overall and individual block diagrams, and using related level and frequency information, a trouble can be quickly localized to a particular assembly. Voltage and signal levels to all assemblies, except the power amplifier, 1A3A1, and front panel, 1A2, may be measured on the mother board, 1A1A1A1, at the appropriate connector or signal point.
After establishing the existence of a trouble in a particular assembly, refer to the servicing information for that assembly located elsewhere in this section of the manual.
Figure 5.1 locates the transceiver component assemblies and modules. Figure 5.2 shows the locations of the rear panel assemblies and components.
5.2 PC BOARD REPAIRS
5.2.1 REMOVAL AND REINSTALLATION
Care should be used when removing PC boards from the transceiver. The card extractor, P/N 600268-618-001, should be used if possible. If no card extractor is available, a temporary substitute can be made from a porary substitute can be made from a length of solid heavy gauge wire (#10-#12). Form a hook at each end of the wire, and then insert each hook into the holes provided at the top outer edge of each PC board. Apply gentle upward pressure near each hook to free the board(s) from their edge connectors.
NOTE
DO NOT USE PLIERS OR SCREWDRIVERS TO REMOVE THE BOARDS.
When replacing boards into sockets, insure that the board is in its proper position in the card guides at each board edge. Apply light downward pressure to the top edge of the board until it is fully seated into its edge connector.
5.2.2 SOLDERING
To avoid damaging the PC boards during the replacement of components, extreme care should be used in soldering and component removal. A low wattage soldering iron (25-50 watts) with a narrow tip should be used.
A low wattage iron is necessary to prevent the application of excessive heat to the copper foil of the PC board. Excessive heat may cause the foil to separate from the board, rendering the board unrepairable. Only a high quality electronic grade rosin solder should be used in making repairs.
CAUTION
DO NOT USE AN ACID CORE SOLDER.
Due to the circuit density on the boards, solder "bridges" or short circuits between adjacent foil runs are possible, if care is not used during soldering operations. After soldering is completed, the area around the connection should be closely inspected for excess solder or "bridges" between adjacent runs or connections. Any "bridges" or excess solder between connections must be removed before reinstalling the board. Because of the double sided construction used on the PC boards, a component lead may be soldered to printed circuit areas on top and bottom of the board. Consequently, when a component lead is removed, the replacement component should be resoldered top and bottom as applicable.
5.2.3 CMOS DEVICE HANDLING PRECAUTIONS
CMOS devices maybe damaged by static voltages, and therefore the following is recommended:
a) All MOS devices should be placed on a grounded work bench surface, and the repair operator should be grounded prior to handling MOS devices, since a person can be statically charged with respect to the work bench surface.
b) Nylon clothing should not be worn while handling MOS circuit or devices.
c) Do not insert or remove MOS devices from sockets while power is applied.
d) When soldering MOS devices, insure the soldering iron used is a grounded type.
5.3 ASSEMBLY AND SUBASSEMBLY IDENTIFICATION
Table 5.5 and Fiqures 5.6 and 5.7 list and identify the assemblies and modules used in the transceiver. Figures 5.8 and 5.9 are interconnection/wiring diagrams for the transceiver. Schematics for each assembly and module, parts lists, and circuit descriptions are contained in this chapter of the manual.
5.4 COVER REMOVAL
To remove the top from the transceiver, unsnap the two fasteners on each side of the cover, and pull the cover away from the front and rear panel.
The top inner cover can be removed by first removing the eight (8) mounting screws that secure the inner cover to the chassis. See Figure 5.3.
5.5 TRANSCEIVER ALIGNMENT AND ADJUSTMENT
As all modules and assemblies of the transceiver are of high reliability, solid state design, adjustments and alignment is seldom, if ever, required. If a module or component replacement or performance indicates the need for adjustments or alignment, the following tables and procedures are provided.
Before performing adjustments, it is recommended that Section 4, Functional Description, and Figure 4.1, the block diagram be reviewed for a more complete understanding of the transceiver.
5.5.1 PRELIMINARY TO RECEIVE ADJUSTMENTS
(See Table 5.1 for recommended test equipment.)
Before performing adjustments on the transceiver:
a) Remove the transceiver key inter lock by removing the accessory connector, plug 1A3-P22, from the rear panel. This removes the jumper between pins "C" and "G" (ground), thereby preventing the transceiver from being unintentionally keyed.
b) Connect an RF signal generator (HP 8640B or equal) to the antenna connector of the transceiver, 1A3-J31.
c) Set the generator frequency and output as listed in Table 5.2. See Figures 5.1 and 5.4 for the locations of the modules and adjustments.
d) Audio output may be measured by an audio voltmeter (HP 400LR or equal) connected to the 600 ohm receiver output (1A3-J2l, pins "A" and "J").
e) To make some of the adjustments on the assemblies, it is necessary to use an extender card (optional equipment, part number 601198-536-001).
5.5.2 PRELIMINARY TO TRANSMIT ADJUSTMENTS
a) Reinstall accessory plug, 1A3P22, on the transceiver rear panel.
b) Connect a 50 ohm, 200 watt resistive load to the transceiver antenna jack, 1A3-J31.
c) Connect an oscilloscope (minimum 30 MHz bandwidth) and an RF millivoltmeter/voltmeter across the 50 ohm load. A 100:1 resistive divider is recommended as RF voltages up to 90 VRMS may be present at the 50 ohm load.
5.6 LOGIC INTERPRETATION
Several types of digital devices are used in the transceiver. The following descriptions are presented to explain their basic operation and symbolic notation. The digital devices used (gates, flip-flops, inverters, etc.) are binary in nature, that is, the output voltage of each can be only in two permissible states. The two possible states are called logic "1" and logic "0". The assignment of voltage levels to these states is arbitrary. However, in this manual positive logic is standardized, which means we define the logic states as shown below.
The flip-flop is a memory device that stores a logic state. The above symbol is that of a J-K flipflop. The state of which is referred to by the level of the Q output. If, for example, the Q output is high, the FF (flip-flop) contains a 1. The Q (Q NOT) output is always the opposite of the Q output. The state of the FF can be changed in two ways. It can be changed by means of the clock input, or by the PRESET and CLEAR inputs. The effect of an applied clock pulse on the state of a FF depends upon the J and K inputs. The J input must be high for a clock pulse to cause a 1 output. The K input must be high for a clock pulse to cause a 0 output. If both J and K inputs are high, the FF toggles (changes state) on each applied clock pulse.
The PRESET and CLEAR inputs operate independently of the clock. A high level input to the PRESET line drives the FF to a level 1, while a high input to the CLEAR line drives the FF to a level 0. Some circuits PRESET or CLEAR with a low level input instead of a high level. This is indicated by a "circle" at the appropriate input terminal.
5.6.5 MICROPROCESSOR
The microprocessor is basically a small computer contained within an integrated circuit. This is a device that can store, retrieve, and process data. They are manufactured in many different configurations. The microprocessor, used in this transceiver, contains an 8 bit central processor unit, a 64 byte on chip RAM, 27 input/output lines, and an internal clock. It is configured in a 40 pin dual in line package.
5.6.6 INPUT/OUTPUT PORT (8 BIT LATCH)
The input/output port is an interface device for use with a microprocessor. It contains, within one package, a large number of gates, buffers, and flip-flops. They are manufactured in many different configurations. The in/out port used in this transceiver is configured in a 24 pin dual in line package.
5.6.7 RAM
Random access memories are logic elements that can be reprogrammed over again many times, and the information stored, can be retrieved by utilizing read/write, and address inputs. A 1024 bit CMOS RAM is used in the transceiver memory system for reliability and low power consumption. It is configured in a 22 pin dual in line package.
5.6.8 INPUT/OUTPUT EXPANDER
The input/output expander is an interface device for use with a microprocessor. The function of which is to increase the pemissible number of inputs and outputs to the microprocessor. It contains within one package, a large number of buffers,
latches, decoders, and other logic circuitry. TWO I/O expanders are used in the transceiver. They are configured in 24 pin dual in line packages.
to increase the permissible number of inputs and outputs to processor. It contains package, a large number of buffers,
latches, decoders, and other logic circuitry. Two I/O expanders are used in the transceiver. They are configured in 24 pin dual in line packages.
5.7 MOTHER BOARD, 1A1A1A1
This board, Figures 5.10, 5.11, 5.12, 5.13 and 5.14, is the electrical main frame of the transceiver. All subassemblies in the transceiver, with the exception of the meter board, 1A2A2, and resistor boards A and B, 1A2A3 and 1A2A4, are electrically connected to the mother board. A total of 24 connectors interface the subassemblies to the mother board. All connectors are of the positive locking quick disconnect type, thus assuring fast and efficient module service or replacement. All electrical components (excluding connectors and filter capacitor C52, are located on the bottom side of the board for easy access,
5.7.1 RECEIVER PROTECTOR
This circuitry, Figure 5.10, located on the mother board, serves to protect the receiver input from excessive RF voltages, Refer to the mother board schematic, Figure 5.11. The receiver protector consists of pin diodes CRI, CR2, CR3, and CR4, 6.2V zener diode CR5, resistors R1 thru R4 and inductor L23. Receiver input signals are applied to the high pass filter board, 1A1A4--14, pin 42. Connected in parallel with this input via R4, are diodes CRI and CR2, and in parallel reverse are diodes CR3 and CR4. Diodes CR3 and CR4 are in series with Zener diode CR5, which establishes the cathodes of CR3 and CR4 at +6.2 VDC. Resistors R2 and R3 forma voltage divider which, via inductor L23, references the anodes of CR3 and CR4, and the cathodes of CR and CR2 to +3.1 VDC. Thus all four pin diodes are reverse biased at a potential of +3.1 volts. The RF input voltage amplitude to the high pass filter is therefore limited to 3.1 volts maximum negative or positive. If this amplitude is exceeded, diodes CRI and CR2 or CR3 and CR4 will conduct, thereby protecting the receiver front end.
5.7.2 MOTHER BOARD ACCESS AND REMOVAL
All components on the mother board, except connectors and filter capacitor C52, are located on the bottom side of the board, thereby providing complete access to these components, by removal of the transceiver bottom cover and motherboard bottom shield. Removal of the mother board assembly, 1A1A1A1, should rarely be necessary. If the need for mother board removal should occur, the mother board can easily and quickly be removed as follows:
a) Remove the front and rear panel assemblies, 1A2 and 1A3, by removing the mounting screws (two on each side of each panel) that secure the panels to the chassis and unplug each panel assembly from the mother board.
b) Remove each subassembly from the mother board, Remove the twelve (12) screws that secure the mother board to the chassis assembly, 1A1A1 (four screws are located on each side of the board and four screws are located in the middle of the board).
c) The mother board should now be completely detached.
d) To reassemble, reverse the pre ceding steps.
5.8 HALF OCTAVE FILTER BOARD, 1A1A2
5.8.1 GENERAL
This board, Figures 5.15/16 performs part of the receive mode preselector function, and in the transmit mode, filters the output of the power amplifier. Located on this board are eight (8) elliptical low pass filters with cut off frequencies of 2, 4, 6, 9, 13, 20 and 30 MHz. Also located on this board are the VSWR detector, ALC detector and amplifier, ACC detector and amplifier and via feedback from the power amplifier assembly, 1A3A1, circuits that will protect the solid state PA from conditions of VSWR, over current, over voltage and over temperature.
The desired elliptical filter is selected automatically by relays which are controlled by ground signals from the logic board, 1A1A9. In the transmit mode, these filters reduce the harmonic output to better than -50 dB. In the receive mode, these same filters attenuate signals that are above that of the desired band of operation.
5.8.2 DETAILED DESCRIPTIONS
5.8.2.1 Filters
The different filters are selected by grounds being applied to pins on the interface connectors. For example, band 1 (B1) is selected by a ground on pin 24. This causes Q12 to conduct, placing 11 - 13 VDC on the coils of relays K15 and k16, causing them to energize. When energized, the RF power is routed through L15 and L16. Note that all other filters are shorted to ground when not being used.
The components in the filters have been optimized to provide an input impedance of 38-62 ohms with a phase angle of less than + 30° when the output is terminated with 50 ohms. This is required in order to provide a low VSWR for the solid state PA. The inductors for bands 1 - 4 are wound on low loss toroid cores, while those for bands 5 - 8 are wound on phenolic forms.
5.8.2.2 VSWR Detector
The VSWR detector consists of transformer Tl, capacitive voltage divider C7 and 28, CR2, CR3, and associated circuitry. Current transformer T1 (single turn primary) produces a voltage proportional to the current in the line. It is heavily loaded by R5 and R6 to flatten its frequency response from 1.6 to 30 MHz. Capacitive divider C7 and C8 samples the voltage on the line and adds it to the current sample voltage at the junction of R5 and R6. Therefore, the voltage applied to the anodes of CR2 and CR3 is the vector sum of the current sample and the voltage sample. The transformer is phased such that the voltage sample and the current sample add together for CR2 (forward power) and subtract for CR3 (reflected power). When the voltages from the current sample and the voltage Sample are in phase and equal in magnitude, the reflected DC output (CR3) is minimum and the forward DC (CR2) is maximum. The component values are selected so the sample voltage phase and magnitudes are equal when terminated with 50 ohms with no phase angle. The Pr DC output is fed to the base of Q3 to reduce the PA drive for VSWR conditions. The Pf DC output is fed through R8 to pin 10 of P16. It is used to drive the front panel meter in the transceiver to indicate transmit power. (The DC voltage for the reflected power indication is supplied by the automatic antenna coupler, if used.)
5.8.2.3 ALC Detector and Amplifier
R1, R2, CRI, Q1 and associated components are used to provide a DC voltage proportional to the peak value of the RF passing through the VSWR detector. The output line (125 watts) (pin 38, P16) is sampled by resistive divider R1 and R2. Capacitors C1 and C2 are used to compensate the AC sample applied to diode CRI. This compensation is necessary to decrease the ALC sample at the higher frequencies and allow more drive to the PA. C2 is normally adjusted to provide 125 watts CW power at 29.9 and 1.6 MHz. The AC sample is rectified by CR1 and fed to the base of Q1. The DC output from Q1 is fed to pin 41 of P16. In the transceiver, the ALC voltage is fed to the transmit modulator and controls the TGC voltage. 125 watts (79 VRMS) generates a DC voltage of 5.5 to 6.5 volts. R4 and C6 provide the ALC time constant. R4 is used to provide a fast rise time for the ALC voltage.
5.8.2.4 ACC Detector and Amplifier
The ACC detector and amplifier consists of R9, R10, CR4, CR21, CR5, R13 and Q2. A sample of the voltage on the line is generated by resistive divider R9 and R10. Frequency compensation of the sample is accomplished by C51 and C53. Voltage doubler C52, CR21 and CR4 rectify the AC sample and drive R12. CR5 is a zener diode that is used to clip modulation peaks when operating AME. This prevents downward modulation of the carrier. The clipped DC sample is applied to R13, which is used to set the level of AM carrier.
Transistor Q2 is the ACC amplifier and is a FET. It is cut off in the absence of ACC sample by two volts applied to the source by resistive divider R16 and R20. The gate of Q2 is driven from R13 through R14. C56 and C57 are RF bypasses. An external ACC voltage can be fed to Q2 from pin 16 of P16. This is used when the transceiver is driving an external amplifier and the drive from the transceiver must be reduced. The output from the ACC amplifier (Drain) is fed to pin 20 of P16. The ACC line is fed to the transmit modulator board in the transceiver and when the voltage on this line is reduced, the drive to the PA is reduced.
Transistor Q4, along with R22, R23, CR8 and R24 is a switch that disables the ACC amplifier when the transmitter is conditioned to any mode other than AME. The gate voltage of Q2 is shorted to ground any time the AMT line is not at logic 0.
Q3, Q14 and Q13 and associated circuitry are used to protect the solid state PA from conditions of VSWR, OC, OV and temperature. A VSWR fault causes an output from CR3 in the VSWR detector. This DC is applied to the base of Q3. When Q3 conducts, its collector voltage decreases from +8 VDC, causing CR7 to pull down the ACC line, decreasing the drive to the PA. In a similar manner, OC or OV DC inputs to pins 22 and 24, respectively, will cause a decrease in the ACC voltage. The TEMP sense input (pin 39 of p16) must exceed approximately 3 VDC to cause 03 to conduct. This delay the heat sink temperature to rise to 90°C before the transmitter drive is reduced. R18 is the TEMP sense adjustment and is normally adjusted to 0.2 volts at TP3 at 25°C. Q14 is a switch that when saturated, will cause the fault lamp to be illuminated on the front panel of the transceiver. The fault light will be turned on for severe conditions of VSWR, OC, OV or TEMP when the ACC line is pulled down to less than 3.5 VDC.
5.8.2.5 Miscellaneous Components
The 0.1 microfarad capacitors, such as C66 through C69, are RF bypasses to prevent RF on the band lines from adversely effecting circuitry on the board.
5.9 TRANSMIT MODULATOR BOARD, 1A1A3
5.9.1 GENERAL
The transmit modulator board, Figures 5.17/18 contains the following: speech compressor, balanced modulator, AME carrier insertion circuit, ALC amplifier and control, CW tone gate and 5 MHZ double sideband amplifier. Audio inputs from the front panel (carbon or dynamic microphone) and the 600 ohm audio input from the rear panel are translated into a 5 MHz double sideband signal and then applied to the IF filter board, 1A1A6. Transmit ALC and ACC volt ages are applied to this board for the establishment of the transmitter gain. ALC controls the output in CW, FSK and SSB, whereas, ACC controls the carrier level in AME mode. All transmit audio passes through an audio compressor, which maintains a high average level of output. This ultimately results in a higher averaye level of RF output power from the transceiver. In addition, no microphone level adjust control is normally required. An adjustment is provided to reduce the 600 ohm audio input level, if necessary, when audio levels from accessory or optional equipment exceeds the recommended 0 dBm audio input levels. An audio gain adjustment, R96, is provided for applications when the audio compressor is disabled or additional microphone amplifier gain is required.
5.9.2 DETAILED DESCRIPTIONS
5.9.2.1 Speech Compressor
The speech compressor consists of U1A, U1B, Q2, Q6 and associated components. The compressor accepts a wide range of audio inputs and provides a constant input level to the balanced modulator. The low level microphone is fed from pin 36 through JP1-1 & 2, and R102 to pin 6 of U1A. For carbon microphone operation, JP1 is strapped 2 to 3, and audio is fed from pin 36 through Ll, C37, R59, and C40 to the input of ULB. In a similar manner, the dynamic microphone input is fed from pin 38 through L2, R55, U1A, C36, R60 and C40 to the compressor input. The dynamic input is amplified in U1A to provide the same level to the compressor input as the carbon microphone. The 600 ohm audio from the rear panel is fed from pins 40 and 42 through T1, R1, C50, R58 and C40 to the compressor input. All three audio inputs are passed through the compressor.
One of the audio gates in U3 is used to inhibit the 600 ohm input to the compressor when pin 31, ISB INH line is pulled low. This gate allows the front panel microphone to inhibit the 600 ohm audio when it is desired to overide the 600 ohm data input with the microphone. The ISB INH line is controlled by the front panel PTT line.
JP1 is provided to allow connecting of the carbon microphone input to R102 for using dynamic microphones that have much less output than the standard microphone. The input to R102 is amplified approximately 20 dB more than the input to R55. R96 is factory adjusted for normal modulation with average speech. If more modulation is desired, R96 can be adjusted CW to increase the gain of U1A.
Compression is achieved by monitoring (sampling) the output level of UlB and generating a DC control voltage to control the level of input signal applied to pin 3 of UlB. The sample of the output of U1B is fed through R73 and C43 to voltage doubler CR5 and CR6. The resulting
DC is applied between the base and emitter of Q6. This voltage causes Q6 to conduct, generating a collector current that flows through R7 and causes Q2 to conduct. When voltage is applied to the gate of U2, it acts like a variable resistor, decreasing the voltage that appears on pin 3 of U1B. In other words, the gain of U1B is constant and compression is achieved by attenuating its input. R58, R59 and
R60 are all series with the IC input. As the resistance of Q2 decreases, the voltage division ratio increases, causing less voltage on pin 3. CR4, when Q1 is turned on, cuts off U1B to prevent modulation of the signal when the radio is operating in CW or in the antenna coupler tune mode.
5.9.2.2 Balanced Modulator
U2 is the balanced modulator and generates an upper and a lower sideband with the carrier suppressed. The audio signal is applied to pin 1 through C23 and R39. R39 is an adjustment provided to allow the optimum level of audio to be applied to the modulator. Third LO (5 MHz) is applied to pin 8. The modulator (MC1596) is a monolithic balanced modulator circuit. It consists of an upper quad differential amplifier with dual current sources. The output collectors are cross coupled so that full wave cross multiplication of the two input voltages occurs. The output signal is a constant times the product of the two input signals. R31 is used to balance the carrier to a null at the output, pin 6.
5.9.2.3 5 MHz Double Sideband Amplifier
The output from the balanced modulator is fed through C27 to an amplifier. Q7, Q8 and associated components comprise the amplifier. The amplified output of Q7 is fed to the input of Q8 via C32. C51 and Q10 are used to attenuate the base input to Q8 when operating in the AME mode. When in AME, Q10 is saturated and capacitive divider C32 through C51 reduces the voltage applied to the base of Q8. This action is required to prevent over modulation in AME. R51 is a gain adjustment to set the open loop gain of the transmitter path.
5.9.2.4 Carrier Insertion Circuit
When operating AME, a certain level of carrier must be generated and injected into the transmit path after the sideband filters. Q5, Q14 and Q15 are used to control the amount of carrier injected. When in the AME mode, (TX AM), a logic 0 is placed on pin 33 and Q3 conducts. Q3 collector voltage saturates Q10 (reducing the double sideband output) and also causes Q14 to conduct. The voltage supplied by R17 and R18 to the gate of Q14 is adequate to turn on Q14. When Q14 is ON, carrier is fed through C15, Q14, C17 and to the base of Q5. It should be noted that CR19 causes Q15 to be cut off in the AME mode. Q15 is saturated by R85, R86 and CR20 in modes other than AM. When Q15 is saturated, it shorts out to ground any 5 MHZ leakage that might pass through Q14. The carrier applied to base of Q5 is amplified and fed to pin 39 on the connector. R17 is used to adjust the level of carrier applied to the system. Pin 39 is fed to the IF/filter board and applied to the base of the TGC controlled to the trolled amplifier.
Provision is made for A3A mode of operation. When a logic 0 is applied to pin 5, Q15 is cut off and Q5 is allowed to amplify. An "ACC Override" voltage on pin 9 can turn on Q14 and allow some carrier to be injected. (The ACC override voltage originates on the high pass filter module.)
5.9.2.5 ALC Amplifier
Q13 and associated components com prise the ALC amplifier. The ALC DC sample is detected on the half octave filter board and enters on pin 29. C52, L5 and C16 are used for filtering any RF that might be on the line. R83 is used to set the peak power level. The output of R83 is fed to the gate of Q13. Q13 is cut off in the absence of gate voltage by resistive divider R72 and R90. When the gate voltage of 213 is more positive than the source voltage, it conducts, reducing the drain voltage. The drain voltage of Q13 is the ACC line. This line goes to the half octave filter and connects to the drain of the ACC amplifier. The ACC voltage is fed through the complimentary output pair Q11 and Q12 to pin 19 and 20. This line is the TGC (transmitter gain control) and connects to the IF board. The gain of the transmitter is controlled by one single stage on the IF board. Provision is made for an external ALC voltage when the transmitter is used to drive another unit, such as a 1 kW amplifier. When this occurs, some means must be provided to reduce the 125 watt PA output to a level suitable to drive the kW. The external ALC is derived from the output of the kW and is brought in on pin 27. It is filtered by C57, L6, C30 and fed through CR18 and R84 to the gate of Q13, where it can be used to override the transceiver ALC.
5.9.2.6 ACC/TGC Voltages and Operating Modes
The ACC line controls the TGC voltage. The gain of the transmitter is proportional to the ACC voltage. That is, with 0 ACC volts, the transmitter has no gain and with +5.5 VDC, it has maximum gain. Q13 reduces the ALC voltage in USB while the ACC amplifier on the half octave filter board reduces the ACC voltage in AME. Note that 213 gate voltage is shorted out by CR17 in the AME mode. The source voltage for the ACC line (and the TGC line) is provided by resistive dividers for different modes. When in USB or LSB, the ACC voltage is provided by R5, R26 and R74. The voltage is fed to the line by CR9. (Note that in AME, CR12 shorts out this voltage.) When in the AME mode, the ACC source voltage is provided by R76, R81 and CR11. C54 is used to slow the rise of the ACC line to prevent large over shoots when the transmitter is keyed in AM. When operating in CW, the ACC Source voltage is provided by R75, R80 and CRIO. C53 is used to slow the rise of the ACC line when line when the transmitter is keyed in CW, C53 shapes the leading edge of the CW RF pulse. Note that during the coupler tune mode, CR23 shorts out the ACC voltage supplied through CR10. The three separate source voltages for the ACC lines provide different open loop gains of the exciter for three different modes of operation.
5.9.2.7 CW Operation
To operate CW, a 1 kHz tone is gated into the balanced modulator. This is accomplished as follows: a logic 0 is applied to pin 37. This causes Q1 to conduct. Q1 collector voltage disables USB through CR4 and also provides emitter voltage for Q9 through CR15. With emitter voltage on Q9, a logic 0 on the PTT line (pin 30) will cause 09 to conduct. Q9 collector voltage, through R8 turns on the two audio gates. (When pins 13 and 5 rise above 4.5 volts, the gates open.) The 1 kHz tone at pin 25 is gated through pins 1, 2, 3 and 4 of U3 and through C9 to the input of the balanced modulator. CR21. shuts off the 1 kHz tone when the antenna coupler is tuning. The side tone output is taken from pins 2 and 3 of 43 and through R70 to pin 28. R78 is used to adjust the open loop drive level in CW.
5.9.2.8 Miscellaneous Circuitry
Q4 is the transmit switch and when a logic 0 is applied to pins 7 or 8, Q4 collector voltage turns on the 55 MHz double sideband amplifier. Capacitors, such as C10, C11, C12, C14, etc. are RF bypasses to prevent RF from getting into the board.
5.9.2.9 Microphone Selection
The chart below lists four different styles of microphones that can be used with the MSR 8000D. Jumper JP-1 is used to condition the unit for different types of microphones, Two options are available: Dynamic or Carbon. Position 1 to 2 of JP1 (See Figure 5.18) is used for dynamic microphones. Units shipped from the factory are in this configuration. Position 2 to 3 configures the input for carbon microphones. JP1, in conjunction with audio gain control R96, allows the radio to be configured for a wide variety of audio input level.
For certain types of digital encoding equipment, audio compressors can create distortion. Jumper plug JP-2 on the transmit modulator board (Figure 5.18) can be used to disable the compressor. If JP-2 is connected 1 to 2, the compressor will be disabled and the input audio level will have to be adjusted using R96 to produce 0.23-0.27 VPP at 1A1A3-TP1.
5.10 HIGH PASS FILTER BOARD, 1A1A4
5.10.1 GENERAL
This board, Figures 5.19/20, performs part of the receive mode preselection and receive RF amplification. In the transmit mode, the output of the mixer board, lAlA5, is filtered by this board. Contained on this assembly are eight (8) elliptical high pass filters with cut off frequencies of 1.6, 2, 3, 4, 6, 9, 13 and 20 MHz. The desired filter is selected automatically by ground signals from the logic board, lala9. This board also contains a broadcast filter which provides attenuation of greater than 70 dB to broadcast signals (signals below 1.6 MHz), and a very low noise receive RF amplifier. A transmit/receive relay is used to bypass the broadcast filter and RF amplifier in the transmit mode. Additional circuitry located on this board provides analog voltages which are supplied to the transmit modulator board, 1A1A3, to more accurately establish the A3A carrier level on transmit.
5.10.2 DETAILED DESCRIPTIONS
5.10.2.1 High Pass Filters
Band 1 (B1) is switched by CR1 and CR2. When a logic 0 (ground) is placed on pin 41, Q6 is saturated, and 9 volts appears on the collector of Q6. This voltage causes current to flow through L19, L20, CRI, L18, R50, CR2, L15 and R20. CR1 and CR2 conduct, and all the other band switching diodes (CR3, CR4, CR5, and CR6, etc.) are back biased. If band 1 is selected in receive, the signal flow is as follows: RF input on pin 42, through k1, C106, CR1, C44, 245, C46, CR2, K1 - pin 8, 2, and through C27 to the broadcast filter. The RF amplifier provides about 4 dB of gain (1.6 - 30 MHZ). The output is taken from T1 at pin 11 of P14. Operation of any other band is similar. During the transmit mode, K1 is energized and the signal flow is as follows: RF input to pin 5 of P14, through K1 (pins 3 and 8), through the band selected, through K1 (pins 2 and 7) and out on pin 25.
5.10.2.2 RF Amplifier
The RF amplifier is used in receive only, and consists of Q4 and Q5. Q5 is a high level FET used in the grounded gate configuration for best intermodulation performance. Q4 is used to provide a constant current source for Q5.
5.10.2.3 Transmit Switch
Q2 is a switch used to energize K1 when in the transmit mode. When a ground (logic 0) is placed on pin 7 and 8, Q2 collector voltage pulls in k1. Q2 collector voltage is also connected to the solid state PA to switch on the PA biases during transmit.
5.10.2.4 A3A Control Voltage
When the A3A transmit mode is desired, a band switched analog voltage is required. The A3A control voltage consists of R8, R10, Q3 and R46 thru R49. When A3A is desired, a ground is placed on pin 31. This cuts off Q3, allowing the voltage on R10 to appear on pin 9. Pin 9 is connected to the transmit modulator board and allows some carrier (-16 to -18 dB) to be inserted in the A3A mode. If band 1 or 2 is selected, CR33 or CR34 conducts, causing 9 volts to be applied across R49. R49 is adjusted to provide proper amount of carrier for 1.6 - 30 MHz. In a similar manner, R48 is adjusted for 3 - 13 MHZ.
Band 7 (13 - 20 MHz) carrier injection is controlled by R47. R46 controls band 8 (20-30 MHz).
5.10.2.5 Overall Gain or Loss
In the receive mode, the overall gain is +1 dB to +4 dB, depending on the band selected. The loss during transmit is -1 dB to -3 dB.
5.10.2.6 Broadcast Filter
The broadcast filter is used only in receive and provides approximately 35 dB additional attenuation to the broadcast band. The overall rejection of the broadcast band is approximately 70 dB. (6 dB cut off frequency approximately 1.4 kHz.)
5.11 HIGH LEVEL MIXER BOARD, 1A1A5
5.11.1 GENERAL
The High Level Mixer Board is interchangeable with the Mixer Board, 601075-536, used in the MSR 5050, MSR 8000 and MSR 6700. In receive mode it converts a 0 to 30 MHz RF input to a 1st IF of 59.53 MHz and subsequently a 2nd IF of 5 MHz. In transmit mode it converts a 5 MHz input to 59.53 MHz and then to RF outputs of 1.6 to 30 MHz. All circuit interfaces are at 50 ohm impedance levels.
Figure 5.21 is a functional block diagram of the board. In receive mode, inputs on the RX input are selected by the RF switch and filtered by the 30 MHz LP filter. The 1st mixer, with an amplified LO input of +21 dBm, 50.53 MHz to 89.53 MHz, converts the RF signals to a 59.53 MHz IF. The mixer is provided a broadband IF termination by a lossless constant resistance network and a non-reflective crystal filter network. A bilateral amplifier provides 18 dB gain which is controllable by a delayed AGC input of 0 to 9 volts. A second crystal filter at 59.53 MHz controls spurious responses due to the second mixer, and complements the selectivity of the first filter and the system information filter for a total 120 dB ultimate selectivity. The second mixer, with an amplified LO of +10 dBm, converts the 59.53 MHz signals to a 5 MHZ IF. The second LO amplifier may be gated off by 9 volt pulses to accomplish noise blanking.
In transmit, the signal path is reversed with inputs at the 5 MHZ IF converted to a 59.53 MHz IF, and amplified by the reversed bilateral amplifier. The RF switch directs the 1.6 to 30 MHz outputs from the 1st mixer to the TX amplifier to produce outputs to +15 dBm.
5.11.2 DETAILED DESCRIPTIONS
5.11.2.1 RX Control
With a TTL low at pins 15 and 16, Q8 saturates putting +9V on all RX functions.
5.11.2.2 RF Switch
CR1 is biased to conduction by the current through R1 with L1 and L2 providing a high impedance to the signal path for RF signals. The resulting voltage across R1 biases CR2 off, isolating transmit circuits from the signal path. The input signals are thus conducted through C1, CR1 and C3 to the low pass filter.
5.11.2.3 Low Pass Filter
The Low Pass Filter is a 7-element elliptical design (C4 through C8, L3 and L4) with a cut off frequency of 31 MHz. This filter attenuates out of band spurious signals in both receive and transmit.
5.11.2.4 First Mixer
Signals from the Tow Pass Filter are applied to pin 1 of the first mixer, MX1, a high level double-balanced diode mixer. These signals (0-30 MHz) are modulated with +21 dBm LO signals )59.53 to 89.53 MHz) applied to pin 8 to produce a first IF of 59.53 MHz at pins 3 and 4.
5.11.2.5 Constant Resistance Network
The Constant Resistance Network provides a 50 ohm load to signals from the mixer at frequencies much greater than the IF frequency. R17 provides the 50 ohm load at high frequencies when C30 is short, and at low frequencies when L14 is short. C29 and L1 are series resonant at 59.53 MHz to couple the signal to the 90° hybrid network thus maintaining a 50 ohm load at frequencies near the 59.53 MHz IF.
5.11.2.6 90° Hybrid/Filter Network
This circuit maintains a 50 ohm impedance by phasing equal mismatches from the two identical crystal filters FL1 and FL2 so that they cancel at the circuit input and add across R18 at an isolated port. T3 with C31 and C32 form a quadrature hybrid tuned broadly to 59.53 MHz at a 50 ohm impedance. This circuit splits inputs from L13 to equal outputs at L15 and L16 phased 90° apart. L15 and C33 match the 2.3k ohm filter impedance of FL1. L16 and C34 perform the same function for FL2. Matching back down to 50 ohms is accomplished by L19, C35 and L20, and C36. L17 and L18 are used to tune the residual capacitance across the filters to increase the ultimate rejection. A second 90° hybrid (T4, C37 and C38) adds the signals from each filter. The total loss through the whole hybrid/filter network is typically 3.5 dB.
5.11.2.7 Bilateral Amplifier
The Bilateral Amplifier consists of receive (Q9) and transmit (Q10) amplifiers activated by a 9 volt RX or 9 volt TX control signal. These amplifiers switched into the signal path by CR5, CR9 or CR10, and CR7 allow reverse signal flow in transmit applications since all other circuits are inherently bilateral.
The amplifiers are feedback controlled to maintain a 50 ohm input/ output impedance with gain controlled by feedback resistor impedances and the relatively low broad band collector output impedance of 600 ohms.
In receive, the signal flows through C38, CR5 (biased on through L23) and C44 to Q9. Q9 is biased by R21 and R22 with R2l also serving as a feedback resistor. The gain is set to 18 dB by the ratio of the collector load of 600 ohms and the emitter resistor R23. 125 and C45 match the 600 ohm output to 50 ohms with the output routed through pin diode CR9. The bias through switches CR5 and CR9 produces an 8 volt drop across L21, R20 at the input and L30, R30 at the output which reverse biases transmit path pin diode switches CR7 and CR10. The maximum signal level for strong signals is limited by a delayed AGC (DAGC) signal from pins 39 and 40. The DAGC input (0 to 9 volts) biases shunt pin diodes CR4 and CR8 which attenuate the signal at 09 input and output for a total of 40 dB at 0 volts DAGC, Bias current is limited by resistors R31 and R29. CR11 delays the output attenuation for optimum linearity. The DAGC circuit is necessary to maintain in-band intermodulation rejection of 30 dB at high input signals. The DAGC attenuation varies from 1 dB at 8.3 volts to 40 dB at 0 volts.
In transmit, the circuit of Q10 is connected through CR7, CRIO by the bias produced through L24, L29 by the 9 volt TX signal. The circuit is identical to that of 99 except for the values of R26 and R28 which produce a 16 dB gain.
5.11.2.8 Crystal Filter
A second crystal filter F13 at 59.53 MHz is required to reject spurious responses due to the second conversion especially the second IF image at 49.53 MHz. This filter, identical to FL1 and FL2, is matched to 50 ohms input and output by L31, L33 and C55, C56 with ultimate rejection improved by L32.
5.11.2.9 Second Mixer and 5 MHz Filter
The 59.53 first IF signal is converted to a second IF of 5 MHz by a second double-balanced diode mixer, MX2. The 5 MHz output signal is filtered by a 5 MHz low pass filter C62, C63, L36 to reject the 59.53 MHz IF Feedthrough, the 54.53 MHZ second Lo and other undesired mixer outputs,
5.11.2.10 First LO Amplifier
The first LO amplifier produces a +21 dBm signal at MX1 (pin 8) from 0 dBm board inputs from 59.53 to 89.53 MHz at pin 3. Q5 and Q6 are common gate FETS paralleled for a 50 ohm broadband input with a transconductance to produce a 6 dB gain into the 50 ohm load produced by T2, The FETS are self-biased to 10 mA by R16. L8, L9, and C20 form a 40 MHz high pass filter to reduce low frequency LO noise.
Q4 is a grounded emitter amplifier with a 15 dB gain which produces the +21 dBm LO signal required by MX1. Q3 is a bias regulator which maintains the voltage drop across R14 (due to the current of Q4) constant by controlling the base current of Q4 through R15. L12 and C28 broadly tune the output for a relatively flat response from 59.53 to 89.53 MHz. Biased at 100 mA, the amplifier can produce a linear output of 250 milliwatts.
5.11.2.11 Second LO Amplifier
Q11 and Q12 are paralleled JFET'S which produce a +10 dBm output at MX2, pin 8 from a 0 dBm 54.53 MHz second LO input at board pin 41. The FETS are self-biased by R32 to 10 milliamperes. L35 and C12 match the 50 ohm level of MX2 to 1.2k ohm at the FET drain to produce a 10dB gain. With a 9 volt input at board pin 37, Q13 produces an 8 volt bias across R32 which cuts the LO amplifier off (cutoff voltage of Q11, Q12 is 6.5 volts maximum) which in turn cuts the mixer off and thus breaks the signal path. This is used as a noise blanker gate in the MSR 8000 and may be used as a transmit inhibit gate in transmit applications.
5.11.2.12 Transmit Amplifier
Q1 and Q2 are feedback controlled amplifiers which increase the level of signals from the first mixer, MX1, to +17 dBm outputs, 1.6 to 30 MHz at board pin 6. Signals from the mixer, MX1 are routed through the low pass filter (C4-C8, etc.), C3, CR2, C14, and C15 to the base of Q2. Q2 is biased for 2.9 volts at the base by R9, RI0, and R11. R7 and R8 produce 30 milliamperes bias current, with R7 setting the gain and R9 controlling the input/output impedance of 50 ohms. Q1 is the identical circuit with values changed to produce a capability of 160 milliwatts linear output. In addition, the base bias is altered to add CR3 which compensates for bias changes with temperature.
5.11.2.13 DC Control
+13 VDC is supplied through L30 to the first Lo amplifier circuit. For installations where 13 volts is not connected to the board, CR6 allows the 9 volts to operate the LO circuit at a slightly reduced level. Grounds on pins 7, 8, or 15, 16 saturate the 9 volt TX or 9 volt RX transistor switches (Q7 or 08) to supply 9 volts to the appropriate circuits.
5.12 IF FILTER BOARD, 1A1A6
5.12.1 GENERAL
The IF filter board contains the three 5 MHz information filters and amplifiers used in both transmit and receive modes. These filters are: FL1 - upper sideband operation, FL2 - lower sideband operation and FL3 - AM operation. The appropriate filter is selected by diode switching via mode information from the logic board, 1A1A9. During the receive mode, a 5 MHz IF signal from the mixer board, A1A5, is passed through the appropriate IF filter and further amplified in three stages. The gain of the IF output is adjustable. An AGC voltage is applied from the audio squelch board, 1A1A7, to two of the IF amplifier stages to reduce the IF gain on very strong received signals.
During the transmit mode, a double sideband signal from the transmit modulator board, 1A1A3, is applied. The appropriate filter will remove the unwanted sideband of the transmitted signal. The signal is then amplified and applied to the mixer board, 1A1A5. Other circuits on this board include an amplifier com biner, U3A, which applies carrier for AME operation, and DC switches Q1 and Q2 which apply voltages to the appropriate transmit or receive amplifier stages. Figures 5.24 and 5.25 show the assembly and schematic of this board.
5.12.2DETAILED DESCRIPTION
5.12.2.1 Filter Selection
The filters are selected by placing a ground (logic 0) on certain pins on the connector, FL1 is used to receive USB and also to transmit USB. (The pass band is on the lower side of 5 MHz, but the signal is transferred to the high side in the mixer.) When USB is selected, a ground is placed on pin 35 of p10. This action causes current to flow through R36, CR10, L14 and CR4. Diode CR10 is connected to the common receive input line (CR3, C20) and when it conducts, the signal is applied to the input to FL1. In a similar manner, the ground on pin 35 causes current to flow through R37, CR13, L19, L11 and CR4. When CR13 is conducting, the output of FL1 is connected to the common output line (C35, CR15 and CR17).
It should be noted that CR11 and CRI2, used to short out the filter input and output if the filter is not selected, are cut off by R35 and R20. When FL1 is not selected, current through R23, CR11 and CRI2 shorts out the filter input and output. Note also, when FLl is selected, FL2 and FL3 are shorted out. FL2 is selected on pin 37 (LSB). FL3 is selected by a ground on pin 31 (AM). The ground on pin 31 causes Q5 to conduct, selecting the AM filter. During transmit AM (AMT), pin 33 selects the USB operational filter (FL1).
5.12.2.2 Receive Path
The receive input is on pin 36. The input of U3C is matched to 50 ohms by L2 and C3. The signal is amplified by U3C and U3D, the gain of this combination is approximately 20 dB. An ISB output is provided on pin 41 through R1 and C61, The output of U3D is fed through R10, C16 and CR3 to the inputs of the filters. R10 is selected to provide a 50 ohm driving source for the filters. R19 is connected to receive +9 volts through L8 and determines the amount of turn on current through CR3. C4 is used to cancel some inductive reactance and compensate the driving impedance for the filters. The amplified input signal passes through CR3 and the selected filter. At the output of the filters, the signal passes through C35 and CR19 into the input of U1, the first receive amplifier. R38 determines the turn on current for CR19. C73 is a compensating capacitor to provide a 50 ohm load for the filter termination. (C63 and R39 provide the primary filter terminating impedance.)
The filter output is amplified in U1 and U2, which are AGC controlled. The AGC input is applied to pin 12. As pin 12 voltage is increased above +4 VDC, the gain is decreased. The output from U2 is fed to Q3 and 04 for further amplification. The overrall receive gain is set by adjusting R31. 50 uV input will provide 100,000 uV output at pin 5. In the transceiver, R31 is adjusted to have an AGC threshold of 6 to 8 microvolts input to the receiver. The precise setting of R3l is therefore a function of the transceiver front end gain.
5.12.2.3 Transmit Path
The double sideband input to the IF filter board is applied to pin 4 and passes through C38 and CR18 to the common filter input/output line. CR18 is turned on by the voltage on the T line which is at +9 VDC during the TX mode. The transmit double side input passes through the selected filter and through C20, CR2, C15, C14 and to the base (pin 4) of U3A. U3A is a variable gain amplifier, the gain controlled by the TGC voltage applied to pin 42. The maximum gain of U3A occurs when the TGC voltage is 5.5 volts and de creases as the voltage is lowered. During normal transmit operation, the TGC voltage is between 3.8 and 4.2 volts. The filtered double sideband signal is amplified in U3A and U3B and fed to the output on pin 38. This output is used to drive the mixer.
The overall transmit gain from pin 4 to pin 38 is from 6 to 12 dB, depending on the TGC voltage applied during normal operation. R11 is used to isolate the transmit output when two IF boards are used for ISB operation. AM carrier is inserted through C12 to pin 4 of U3A. It should be noted that the ratio of AM and USB is established on pin 4 of U3A and will remain constant because the TGC voltage controls both components of the signal in AME operation.
5.12.2.4 Miscellaneous Circuitry
Q1 is the transmit switch and is activated when a logic 0 is placed on pin 7. The collector of Q1 rises to +9 volts and conditions the board for transmit operation. In a similar manner, a logic 0 on pin 16 causes +9 volts on the collector of Q2 and the board is conditioned for receive operation. Capacitors such as C62, C72, C55, C54, etc. are RF bypasses. L24 is used in the TGC line to prevent feedback from the PA causing transmitter loop oscillation.
5.13 AUDIO/SQUELCH BOARD, 1A1A7
5.13.1 GENERAL
The audio/squelch board, Figures 5.26/27, is used in the receive mode only. This board accepts the 5 MHz IF output from the IF filter board, 1A1A6, and performs the final detector function to convert the intermediate frequency signal into usable audio intelligence. This process involves two discrete, but not simultaneous, detector functions,. A product detector is operative in all modes except the AME mode. In the AME mode, an envelope detector is operative. Two separate audio outputs are provided. A 600 ohm line audio output is applied to the rear panel connector, 1A3J24, and a low level output is applied to the speaker/driver board, 1A1A8, to provide the front panel speaker and headphones/headset audio.
Located on this board are an input IF amplifier, AGC detector and amplifier, AM/product detector, squelch amplifiers and gating circuitry. (In the all modes, AGC voltage is derived from the 5 MHz carrier by CR3 and CR4, and is amplified by Q3. Fast attack, fast decay is used for AM, FSK and CW signals, and fast attack, slow decay is used for sideband signals. AGC voltage to the IF filter board, lalA6, and delayed AGC voltage to the mixer board 1A1A5, controls the receiver gain.
Other circuitry and functions through this board are side tone and mute functions. The rear panel audio (600 ohm) is unaffected by operation of the squelch control.
5.13.2 DETAILED DESCRIPTIONS
5.13.2.1 Input IF Amplifier and AGC Amplifier
Q2 is an input amplifier that accepts the IF input on pin 5, amplifies and drives Q10, an emitter follower. The follower is used to provide a low driving impedance for the AGC detector and the product detector. The output of Q10 is rectified in the voltage doubler C4, CR3 and CR4. The rectified DC, applied between the emitter and base of Q3, causes Q3 to conduct, causing current to flow through R1 and R5. The positive going emitter voltage of Q3 is fed through CR17 to pin 11. This AGC voltage is used to reduce the gain of the IF filter board. The AGC voltage drives Q1 through R5, generating a negative going delayed AGC on pin 40. The front panel meter is driven through R2 and CR2. The delayed AGC is used to control the gain of the mixer and is used for large input signals, R5 is adjusted so Q1 collector voltage is +3 VDC when 100,000 uV are applied at the antenna.
5.13.2.2 Product Detector and AM Detector
The product detector consists of U1A, U1B and U1C. The output of Q10 is fed through C17 to pin 2 of U1A. The third LO, from pin 12, is applied via C16, to the base (pin 12) of U1C. Since U1A emitters are connected in series with U1C, the third LO modulates the current through U1A, causing a mixing action. Audio voltage is developed in the collector circuit (pin 5) and the 5 MHz is filtered by C19. The detected audio is fed through U1B and U1D to drive other circuits. It should be noted that in USB or LSB, the collector load for U1A is R23 in parallel with R22. A logic 0 on pin 35 or 37 will cause Q6 to conduct, applying +9 volts through CR7 and R23. During AM operation, Q6 is cut off and the collector load for U1A is R22 only. Also, the third input is attenuated 40 dB. For AM detection U1A operates as an envelope detector. When Q6 is cut off, R18 causes current to flow through CR1 and R13. This action further reduces the amount of the third LO present during AM operation.
5.13.2.3 600 Ohm Line Driver
The product detector/AM detector output is fed through emitter follower U1B to C39 and R54. R54 is adjusted to provide the proper output on pin 14 and pin 6. The output of R54 is fed through C40 and R53 to pin 6 of U4A, 14A and 27 further amplify the signal and the floating 600 ohm output is developed across T1 pin 1 and 3. It should be noted that the DC input to transformer T1 is on pin 5. 27 current flowing from pin 5 to 4 is balanced by R42 current flowing from pin 5 to 6. This configuration prevents T1 from being saturated by the DC current of T1. The nominal output of the line driver is 0 dBm, but is adjustable to +10 dBm.
5.13.2.4 Squelch Amplifier
The squelch amplifier consists of C20, R25, U4B, Q8, CR9, CR10 and associated components. The audio output from U1B drives through C20 and R25 to pin 3 of U4B. U4B is operated as a variable gain amplifier. The gain variation is achieved by removing negative feedback (reducing negative feedback increases gain) with C23. The front panel squelch (pin 10) applies a positive voltage from +5 to +9 VDC to CR11. This voltage, applied to the gate of Q8, causes Q8 to act as a variable resistor.
As the resistance between the source and the drain of Q8 is lowered, C23 reduces the amount of negative feedback applied to U4B, pin 2, causing U4B gain to increase. Voltage divider R27 and CR16 assures that the source voltage will be greater than the pinch off voltage of Q8. This assures that Q8 will be cut off with no input to its gate. CR14, R35, CR15 and R37 force the anode of CR9 to be more positive when the squelch controls are maximum counterclockwise. This action assures that the audio gate will be open for any signal condition when the squelch control is fully counterclockwise. It should be noted that the feedback network for U4B is frequency selective (R31 and C25) and the amplifier has maximum gain at approximately 300 Hz.
The output of U4B (pin 1) is rectified in voltage doubler C44, CR9 and CRI0. This DC is applied to pin 13 of U2. When pin 13 rises about 4.5 volts, the audio gate opens and audio is passed through to Pin 3. The squelch time constant is determined by C28 and R35. R50 and CR18 act as a clamp to limit the excursion of the audio gate voltage, thereby decreases the decay time of the squelch voltage. The N.B. ON input on pin 28 (+9V) forces the squelch gate to be open anytime the noise blanker is on.
5.13.2.5 Audio Squelch Gate and output Amplifier
U1D accepts the output from the product detector and drives the audio gate, U2. The audio gate can be controlled by the squelch or the audio mute line, pin 32. The audio passes through C46, R38, pin 1 of U2, through SWA, out on pin 2 of U2 and into SWB on pin 3. The Output of SWB, pin 4, drives the base of Q4 through C32. SWA or SWB of U2 can be closed to kill the speaker audio output. A logic 0 on the mute line will cause pin 5 of U2 U2 to decrease to below. +4 VDC and the audio will be killed. The mute line is used to kill the audio during the antenna coupler tuning mode, or any time the synthesizer losses lock (for example, when changing bands). Audio amplifier Q4 can also be driven from the side tone input on pin 27. The side tone input comes from the transmit modulator board and is used during the CW mode to provide aural monitoring of CW keying.
5.13.2.6 Miscellaneous Circuitry
Q5 is the receive switch and is energized when a logic 0 is placed on pin 15. When Q5 is turned on, +9 volts is applied to most circuitry on the board. Note that Q4 is active in transmit as well as receive because of the side tone requirement. Q6 is a DC Mode switch and is turned on in LSB, USB, or FSK.
5.13.2.7 AGC Time Constants
For USB, LSB or AM, the AGC time constant is determined by C3 and R69. When operating in FSK or CW, the time constant is C3 and R59 in parallel with R69. The AGC amplifier has a fast attack and a slow decay. The decay time is decreased in FSK or CW.
The audio passes through C6, R38, pin 1of U2, through SWA, out on pin 2 of U2 and into SWB on pin 3. The output of SWB, pin 4, drives the base of Q through C32. SWA or SWB of U2 can be closed to kill the speaker audio output. A logic 0 on the mute line will cause pin 5 of U2 U2 to decrease to below. +4 VDC and the audio will be killed. The mute line is used to kill the audio during the antenna coupler tuning mode, or any time the synthesizer losses lock (for example, when changing bands). Audio amplifier Q can also be driven from the side tone input on pin 27. The side tone input comes from the transmit modulator board and is used during the CW mode to provide aural monitoring of CW keying.
5.13.2.6 Miscellaneous Circuitry
Q5 is the Receive switch and is energized when a logic 0 is placed on pin 15. When Q5 is turned on, +9 volts is applied to most circuitry on the board. Note that Q4 is active in transmit as well as receive because of the side tone requirement. Q6 is a DC Mode switch and is turned on in LSB, USB, or FSK.
5.13.2.7 AGC Time Constants
For USB, LSB or AM, the AGC time constant is determined by C3 and R69. When operating in FSK or CW, the time constant is C3 and R59 in parallel with R69. The AGC amplifier has a fast attack and a slow decay. The decay time is decreased in FSK or CW
5.14 SPEAKER/DRIVER BOARD, 1A1A8
5.14.1 GENERAL
The speaker/driver board, Figures 5.27/28, contains the four watt speaker amplifier, DC volume control circuit, tuning beep generator and channel number buffers. Audio from the audio/ squelch board, 1A1A7 , is applied to this board through an opto-coupler.
The resistance of this opto-coupler and thus the output of the speaker/driver IC, U3, is a function of the setting of the volume control located on the front panel, 1A2. As the volume control is supplying a variable DC voltage only, hum and noise rejection of the audio amplifier is exceptionally good. The beep tone, when enabled by the function ENABLE/DISABLE switch, 1A1A9-S1-3, causes a dual timer U2 to generate 2 kHz "beeps", as the remote antenna coupler is operated. The amplitude of the beeps can be adjusted by the volume control. The channel number buffers located on this board buffer the BCD channel number information from the logic board, 1A1A9, before it is routed to the rear panel accessory connector 1A3-J25. The audio output from this board drives the front panel speaker, 1A2-LS1, the headphone jack, 1A2-J32, and the audio output pin of the microphone jack, 1A2-J34.
5.14.2 DETAILED DESCRIPTION
The speaker amplifier, U3, is a monolithic audio amplifier in a noninverting operational configuration. Resistor R10 (56 ohms) sets the nominal voltage gain at 71 (37 d3). Capacitors C10 and C11 are compensation capacitors, and C12 and R11 form an output compensation network. Capacitor C7 is a bootstrap capacitor which enables the amplifier to drive positive nearly to the supply voltage. The output, pin 12, is biased nominally at half the supply voltage. The speaker is coupled through C13.
The audio input is coupled to U3, pin 8, through opto-coupler CR3, which contains a photo resistive cell optically coupled to an LED. As the LED current increases, the resistance of the photocell decreases, applying more input signal to pin 8 (U3). "The LED current is limited by R5, and is controlled by the setting of the front panel VOLUME control.
The tuning beep tone burst is coupled to the audio input through R7, which provides attenuation. The tone burst is generated by U2, a dual timer. The timer, whose output is pin 9, generates a 2 kHz tone which is gated off and on by the other timer whose output is pin 5. This timer is set by C3, CRI, CR2, R3 and R2, and is gated on by a high level at pin 4. This signal, called "Beep", comes from the coupler tuning logic.
Integrated circuit U1 is simply an inverting open-collector buffer which relays the channel switch information to the rear panel accessory connector.
5.15 LOGIC BOARD, 1A1A9
5.15.1 GENERAL
The logic board, Figures 5.29/30, supplies frequency, band, mode and channel information to other assemblies and/or optional equipment. This board receives input data from the front panel and/or rear panel accessory connector. This data is processed, and then appropriate commands are applied to other boards in the radio for operation. This is possible because of the microprocessor U1 and other supporting circuitry. In addition, ten channels of memory can be stored by U4. A low leakage lithium battery maintains memory power when operating power is not applied or is removed from the transceiver. Also located on this board is the program ENABLE/ DISABLE switch, S1. This eight section switch allows memory, beep tone, manual control mode of the transceiver and surveillance tune mode of the automatic antenna coupler to be enabled or inhibited.
5.15.2 DETAILED DESCRIPTION
Refer to Figure 5.32 for a block diagram.
U1 is an 8035 microprocessor (uP) with an 828181 PROM (U3) as program memory and an IM 6551 Static RAM as data memory, U2 (8212) is used as an address latch device to latch address information for external program and data memory chips U3 and U4.
Port 2 of U1 (pins 21 through 24 and 35 through 38) are used as input ports to enter emission mode information (pins 21, 22 and 23). Channel information (pins 24, 35, 36 and 37) and TX/RX information (pin 38). Bits 0 and 1 of port 2 (pins 21 and 22) are also used as ninth and tenth bits of address to address up to 1024 locations on external program memory chip U3. Port 2 is also used as an output port. Under this condition, data in the low four bits (pins 21 through 24) are fed to I/O expander chips U5 and U6. Each expander chip provides four 4 bit output ports. The BCD output of each port is applied to the synthsizer to determine the frequency of the radio. U6-P5 controls the 100 Hz digit, U6-P6 controls the 1 kHz digit, and U5-P5 controls the 10 kHz digit. These outputs are applied to the minor loop board, 1A1A13.
U6-P7 controls the 100 kHz digit, U5-P6 controls the 1 MHz digit, and U5-P7 controls the 10 MHz digit. These outputs are applied to the major loop board, 1A1A15.
U5-P4 is the output of special code for emission mode display. The 3 low bits of this code are detected by U18 to provide emission mode command to the receiver/exciter. The output of U18 is disabled (all high) when U18-12 is high (during the coupler tune period). U18 also provides a coupler home signal when the frequency is changed more than 10 kHz or the channel is changed.
U6-P4 contains band information which is detected by U13 to provide band select commands via decoder, U13.
Port 1 of U1 (pins 27 through 34) is used as the output port. Bits 0 through 3 are channel and frequency information and bits 4, 5 and 6 are the display code for the multiple LED digit display.
T0 and T1 input pins (U1-1 and 39, respectively) are the frequency change command inputs with T1 for frequency increasing and T1 for frequency decreasing. INT pin (U1-6) is the load memory command input. When this pin is pulled low, the program is interrupted and jumps to load memory sub-routine.
NAND gate (U14-11, 12 and 13, R5 and C2) are used to extend the trailing edge of the ALE signal so that port 2 of U1 can be used as an input and output port without affecting each other. U4 is a CMOS static RAM with low voltage data retaining capability. When power is turned off, B1 supplies 3 volts through CR1 to retain the data stored in U4.
U4 is a 256 x 4 bits CMOS static RAM that is used to store data for each channel. There are eight 4 bit words for each channel. Words one through six represent the 6 digit frequency (100 Hz's digits through 10 MHz's digits, respectively). The seventh word is band information and the eighth word is emission mode information. The address lines of this chip are controlled as follows: bits 0, 1 and 2 are controlled by software. For each set channel it will be scanned from 0 to 7 to obtain 8 memory locations required for each channel. Bits 3 through 6 are controlled by the channel switch. The MSB (bit 7) is controlled by the TX/RX switch. In the RX mode, MSB ** 0, memory locations 0 through 127 of U4 are selected. For TX, MSB = l, memory locations 128 through 255 are selected.
Transistor switch Q12 is used to stop the uP immediately when Vcc drops below 4 volts to prevent the loss of memory in U4 from occuring.
Whether the transceiver is in the transmit or receive mode is determined by Q5 (TX line) and Q4 (RX line). These are connected so that when U11 pins 11, 3 and 6 are high, Q4 is ON, Q5 is OFF, and the unit is in the receive mode. Q3 drives the AMT line, turning ON when the radio is in the transmit and AM mode. The transmit mode may be caused by only one of pins 11, 3 or 6 going low, For a pin to go low, both of its inputs must be high. Note that input pins 13, 2 and 4 are connected so that if pin 13 is pulled low by U10, pins 1 and 13, the unit cannot go into transmit mode. If the LL (loss-of-lock) line is low, the key interlock line high, or the load memory line high, U10 pin 1 or 13 will be low, inhibiting transmit. Also, U10 pin 10 will mute the audio if either the LL line is low or load memory line is high.
In U11, pin 12 causes transmit during coupler tune, pin l causes transmit from the PIT line and pin 5 causes transmit from the CW delay one-shot, U12, pin 13. If the unit is in coupler tune, U15, pin 15 will be high, so U8, pin 10 will be low, pulling U11 pins 2 and 4 low, which will inhibit transmission from pins 1 and 5.
When the PTT line is grounded, pin 2 of U8 goes high which drives U11, pin 3, low (if pin 2 is high), causing transmit. At the same time, U11, pin 8, will go low causing the microprocessor to recall the transmit frequency from memory. During CW operation, it is desirable to keep the transmitter keyed so that the radio does not go from transmit to receive at the end of every dot and dash. If the CW mode is selected, the collector of Q2 will be high, enabling the CW delay one-shot portion of 112. The one-shot is triggered at the end of each character via C25 as pin 2 of U8 rises. U12 is a retriggerable one-shot, which means that pin 13 stays high for 0.5 to 5 seconds (determined by the setting of R8) after any trigger pulse arrives, even if it arrives while the one-shot is already triggered. When the one-shot is triggered, pin 13 is high, driving U11, pin 6 low, which keeps the radio in transmit for 0.5 to 5 seconds after the last CW character is sent.
A normal coupler tune cycle is initiated by a ground on the LIN line from Q8, via R56, C33, 5S1-6 and Q10, or by the program software, via S1-5 and U16 to supply a logic 0 pulse to U15, pin l. This flips U15, pin 15, high and pin 14 low, turning ON Q6 (TNG line) and turning OFF 09. Since the If the TUNING BEEP switch is on, the beep starts. When U15, pin 15, goes high, it sends a TUNE command (low) to the coupler via U8, pin 8. When the coupler responds with a Key Enable command, Q7 turns off and the collectors of Q7 and Q9 will now rise, putting the radio into the transmit mode via U11, pin 11 (logic 0). At the end of the tune cycle, the TUNING line rises, turning on Q10. This triggers the reset oneshot portion of U12, which resets both flip-flops in U15. Note that if the coupler Enable line is not grounded, Q11 will be on, holding pin 7 at ground. This will hold pin 12 low, which will hold both sections of U15 reset, so a tune cycle cannot be initiated.
When the AUTO-TUNE Switch is ON, U16, pin 5, is low, via inverter U82. When the PTT line goes low, U8-2 goes high causing U16-5 to be high, and this initiates a TUNE cycle. If the channel is changed, or the frequency is changed more than 10 kHz, a short negative pulse appears on U18, pin 9. This pulse is inverted twice by gates of Ul6 and resets U15; pin 15, high and pin 14 low. The tune cycle is initiated by pushing the microphone push-to-talk button. This triggers U15, pins 11 and 15 high, and allows the transmit mode. At the end of the cycle, U15 is reset by TUNING going high. A TUNE cycle cannot be initiated unless S1-5 is closed.
5.15.3 SOFTWARE DESCRIPTION (Refer to Program Flow Chart)
When the system is first turned on, or the channel, emission mode and TX/RX switch changed, the microprocessor will read the channel, mode and TX/RX switch settings. The channel number is the first to be detected and displayed (no channel display in the manual mode). Corresponding data for the set channel is moved from U4 to the uP on chip RAM (user's RAM) location 8 through 15. The up will scan through this data again and again to display frequency and emission mode. Data in user's RAM is used by the up to display frequency and emission mode, calculate the synthesizer's frequency, output band and emission mode commands. In channelized operation, if the load/operate switch is in the "operate" position, the data in the user's RAM cannot be changed for the set channel. However, if it is in the "load" position or in manual operation (channel switch in position 11), the frequency and emission mode can be changed by the control of the front panel switches. New synthesizer frequency and band information will be up-dated by the up and the coupler TUNE signal is sent out if the frequency change is more than 10 kHz. The up-dated information in user's RAM will be stored in U4 when the Load TX or Load RX switch is depressed in channelized operation or will be automatically stored in manual operation. If the TX switch is depressed in the channelized and operate mode, the TX frequency will be shown on the display, and the transmitter will not key. The display TX frequency therefore is not being transmitted.
If invalid frequency or mode data is scanned by the up, a default frequency of 29.9999 MHz and mode of USB will be entered and displayed. This prevents data errors due to a discharged memory backup battery, vehicle electrical system noise, or erroneous memory data entry, causing improper frequency and/or out of band operation.
5.16 POWER SUPPLY REGULATOR ASSEMBLY, 1A1A10 5.16.1 GENERAL
The power supply regulator, Figures 5.33/34, supplies two of the four regulated operating voltages for the transceiver. The two voltages provided by this assembly are +9 volts and +5 volts regulated DC. +12 or +24 VDC from the rear panel power connector, 1A3J30, is applied to the input. U1 and transistors Q1 and Q2 form a +5 volt high efficiency regulator. The voltage output of the 5 and 9 volt regulators are adjustable. The output of the 9 volt regulator is applied to the 1A1A2, 1A1A3, A1A4, A1A5, A1A6, 1A1A, 1A1A8, 1A2 and 1A3 assemblies.
The output of the +5 volt regulator is applied to the 1A1A8, 1A1AI, 1A1A11, A1A12, 1A1A13, 1A1A14, 1A1A15 and 1A2 assemblies.
5.16.2 DETAILED DESCRIPTION
The power supply regulator assembly furnishes regulated +5 volts and +9 volts at high efficiency from any input voltage between 11.2 volts and 30.4 volts. The unit contains two separate supply sections, one for +5 volts output and one for +9 volts output. Since the sections operate identically, only the +9 volt section will be described in detail.
The purpose of U2 is to turn on 23 with the proper duty cycle to establish the correct output voltage. More about U2 later. The key components in a switching supply are transistor Switch 23, diode CR4 (a fast recovery type), storage inductor L3 and storage capacitors C14,
C15 and C16. In operation, Q3 is either on (saturated) or off. When Q3 turns on, the current builds up slowly through L3, while C15-C16 furnish the output current until the current through L3 builds up high enough. When Q3 turns off, the voltage at the junction of L3 and CR4 tries to go negative. When the voltage catches on CR4, L3 continues to supply output current. The efficiency of the power supply is very high because:
1) Q3 is either saturated or off, wasting little power,
2) little power is wasted in CR4 because its drop is small, and
3) current stored in L3 is used during the off cycle.
Integrated circuit U2 is a switching power supply subsystem which contains:
1) an RC oscillator,
2) a pulse width modulator,
3) output drivers, and
4) an error amplifier, over current sense and a voltage reference. The oscillator runs at a fixed frequency determined (40 kHz) by R19 and C11 (U1 is slaved to U2's oscillator via pins 3 and 7). The output drivers (pins 13 and 12) drive Q3 via R2l with a pulse width determined by the width modulator, which receives instructions from the error amplifier. The error amplifier compares a sample of the output voltage on pin 1 with the reference voltage in pin 2. If the sample is lower than the reference, the pulse width increases. If the sample is higher than the reference, the pulse width decreases. The voltage sample is determined by R18, R17 and adjustable trimpot R16. Network C12 and R20 are feedback stabilization components which determine power supply stability and transient response. Over current is sensed by the drop across R23 and set by R24 and R2.
Chokes L7, L6 and L5, along with capacitors C19, C20 and C2l are filters to reduce RFI outside the can. The +9 volt output has as additional ripple filter L4, C17 and c18, and the input has an additional filter L1, C1 and C2. Over voltage protection is provided by zeners CR1 and CR2. If pass transistors Q3 or Q5 should short, CRI or CR2 will hold the output voltage and cause the rear panel radio fuse to blow.
5.17 NOISE BLANKER, 1A1A11
5.17.1 GENERAL
The noise blanker, Figures 5.35/36, is a high gain noise pulse amplifier and detector which is used to gate off the second L that is applied to the mixer board, lala5, thus effectively blanking the receiver during periods of interferring noise pulses such as ignition noise, etc. The input of the amplifier is tuned to 35 MHz (above the transceiver operating frequency). Impulse noise occupies a wide bandwidth and can effectively be amplified and detected at this frequency. Using this frequency prevents saturation of the noise blanker by large signals in the 1.4 to 30 MHz band. The noise blanker input is connected to the output (ANT) of the half octave filter board, 1A1A2. 'The output of the noise blanker is applied to the mixer board, 1A1A5.
5
.17.2 DETAILED DESCRIPTION
The noise blanker is a high gain noise pulse amplifier and detector used to gate off the second local oscillator, thus blanking the receiver during interferring noise pulses such as ignition noise. The amplifier is tuned (by C3, L4 and L6) to 35 MHz in a quiet part of the band to prevent saturation by large signals in the 1.4 to 30 MHz band.
The input at pin 39 is taken from the 50 ohm antenna input line of the receiver. C1, C3, C5 and L1 form a single pole bandpass filter with a bandwidth of about 1 MHz. C1 matches a 50 ohm source impedance to 18K ohms across the filter. The small 4.7 pf value of cl has a negligable effect on the desired signals on the antenna line over the 1.4 to 30 MHz band. It also limits the maximum signal power into the noise blanker during transmit when 125 watts appears on the same antenna line. CRl and CR2 are pin diodes with low capacitance and high offresistance to prevent loading the tuned circuit. They protect the following active circuits. The power to each diode from the 125 watt transmit signal is limited to less than 62 milliwatts in the worst case at 30 MHz by the high source impedance provided by cl. C5 matches the filter impedance down to a 1K ohm impedance (the parallel resistance of R1 and the 3K ohm input of U1). L2 tunes the 7 pf parallel input capacitance of U1.
The outputs of U1 and U2 are tuned to a bandwidth of about 1 MHz each by C8, L4, C12 and L6, respectively. R5 and R6 provide damping for stability. The overall bandwidth of the linear circuitry before detection is about 300 kHz. The voltage gain is about 90 dB to the output of U2. The overall gain can be adjusted by R4, which varies the AGC bias to U1. The 80 dB bandwidth is approximately +5 MHz. The noise figure from a 50 ohm source is about 19 dB, which gives a 10 dB S/N at -85 dBm input.
The amplifier stages are followed by a peak detector (CR4), which is biased by R7 and CR3 to obtain low level detection with temperature compensation. The detector output (monitored at TP3) will show about 0.2 VDC at maximum gain and no signal. A-90 dBm CW input will produce 0.34 VDC.
The detector is followed by a comparator U3, which is biased within its operating range by R9, R10 and R11. The current through R10 pror duces a 20 millivolt drop which input pulses must overcome to produce a positive output from U3. The time constant of C16 and Rl0 produces a differentiator which passes only fast rise time pulses.
The comparator is followed by a dual Monostable multivibrator, Q4. Input pulses from U3 trigger the first multivibrator through pin 4, which produces a +9 volt peak output pulse, with a pulse width of 340 microseconds as determined by R13 and C19. This pulse is used to gate off an amplifier stage in series with the second local oscillator in the transceiver receiver. The pulse width is wider than necessary to compensate for delays and ringing in the norrowband stages which the noise pulse in the receiver path encounters before it is blanked in the second mixer. A second multivibrator section triggered by the output pulse at pin 12, is used to inhibit the first multivibrator for 1.4 milliseconds (as determined by R15 and C20). This prevents the receiver from being completely blocked by triggering from fast PRF (pulse repetition frequency) signals.
The noise blanker is enabled by a ground on pin 21 (as from a front panel switch) and a ground on pin 16 (which occurs in the receive mode).
The noise blanker requires +9 VDC at 42 milliamperes on pin 27 or 28.
5.17.3 CALIBRATION AND ADJUSTMENT
Normally no calibration or adjustment of the noise blanker is required, as the PC assembly is aligned at the factory. IF component replacement or other reasons indicate the need for alignment or adjustment proceed as follows:
a) Remove the transceiver key interlock, by removing the accessory connector, plug 1A3-P2. This removes the jumper between pins "C" and "G" (ground) thereby preventing the transceiver from being unintentionally keyed.
b) Connect an RF signal generator to the antenna connector 1A3-J31. Set the generator mode to CW, frequency to 35.0 MHz and the output amplitude to -80 dBm (.022 millivolts).
c) Remove the noise blanker card from the transceiver, place on an extender card (optional equipment, part number 601198-536-001) and reinstall in the transceiver.
d) Connect a DC VIVM or VOM (nondigital type) between TP-3 (white) and TP-2 (black) ground. Set the voltmeter to a scale capable of reading 0.5 VDC.
e) Apply power to the transceiver.
Turn on the noise blanker from the front panel of the transceiver (pull out on the squelch control).
f) Adjust variable capacitor C3, and variable inductors L4 and L6 for maximum DC voltage indication on the DC voltmeter.
g) Adjust R4 to maximum clockwise position (maximum N.B. gain). The DC voltage at TP-3 should be between 0.29 and 0.41 VDC.
h) Disengage the RF signal generator. Proper N.B. operation may be verified by applying a source or simulated source of impulse type noise to the antenna input of the transceiver. This noise source may be a pulse generator adjusted to the following: pulse width l microsecond, pulse amplitude 8 mVPP, pulse rise time 10 nsec. nominal, and pusle repetition frequency (PRF) of 100 pulses per second.
i) Connect an oscilloscope to the output of the noise blanker, pin 9. The output should consist of 240-440 microsecond pulses of
approximately 9 volts amplitude. j) As the pulse generator or impulse
noise source is removed, the pulse output of the noise blanker ceases.
k) This completes the checkout and test of the noise blanker, 1A1A11.
1) In locations of the high ambient impulse noise (such as industrial complexes, etc) if such noise sources cause erratic triggering of the noise blanker, the condition may be improved by decreasing the gain of the noise blanker. This may be done by engaging the noise blanker, and then turning R4 counterclockwise to de crease the noise blanker gain until more satisfactory operation occurs. The noise blanker is still highly effective, even with its gain reduced.
5.18 REFERENCE BOARD, 1A1A12
The reference board, Figures 5.37/ 38/39, contains the 5 MHz temperature compensated crystal oscillator (TCXO), from which are derived the 50 kHz reference for the major loop, the 1 kHz reference for the minor loop, the 1 kHz CW tone and the 5 MHZ third Lo signal. This board also contains the clarifier oscillator and a +24 volt bias supply for the major loop.
The TCXO output at 5 MHz is buffered by a NAND gate (U2, pin 8). An external reference input (U2, pin 9) is available for possible future uses of this board where the reference oscillator might be mounted remotely. From U2, pin 8, the 5 MHZ splits into two paths. One goes to the third LO switch, pin 1 of 42. The other goes to U1, a dual decade counter, which is connected to divide-by-100. The output of U1 on pin 3 is buffered by U6, pin 8, to become the 50 kHz reference signal to the major loop board. The 50 kHz signal also drives the voltage multiplier from U6, pin 11. Transistors Q1 and 22 are high current drivers which drive the voltage multiplier with a 50 kHz square wave of approximately 11.5 volts peak-topeak amplitude. Diodes CR2 through CR6 and associated capacitors form a voltage multiplier. The output is regulated to +24 volts at TP1 by zener CR1, and is designed to supply approximately 2 mA to the major loop board.
The AM and RX lines are buffered and inverted by Q4, Q5 and associated circuitry, and routed to pins 4 and 5 of U2. If the transceiver is in AM receive, the AM and RX lines will both be low, so pins 4 and 5 of U2 will both be high. This drives pin 6 (U2) low which makes pin 3 high, inhibiting the third LO output. Transistor Q3 is an emitter-follower which drives the third LO output through a harmonic filter made up of L12, L6, L7, L11 and associated capacitors. The third LO output level is adjustable with R9. The output level is normally set to O dBm (.224 volts RMS).
The clarifier shifts the receive frequency by substituting a variable 1 kHz reference for the fixed 1 kHz, which normally supplies the minor loop. The clarifier oscillator, 26, is a Colpitts configuration crystal oscillator whose operating frequency is determined principally by yl, L10 and varicaps CR13 and CR12. The CLARIFIER control on the front panel varies the bias on the varicaps from 0 volts to +9 volts. This causes the frequency of the nominally 5 MHZ oscillator to shift at least +1250 Hz. The output is buffered by Q7, which drives U4, a dual decade counter which is connected to divide by 100 and gives a 50 kHz output at pin 9. The clarifier will be ON only if the RX line is low and the CLRS (clarifier switch) line is low. If this is true, U2 pins 13 and 12 will be high, pin 11 will be low. This disables the pin 11 gate of U3 and enables the pin 6 gate of U3. Since pin 3 is high, Q8 is turned on, which enables the clarifier oscillator. The 50 kHz at U3, pin 8, is now being supplied by the clarifier oscillator rather than the TCXO. U5 is connected to divide by 50 to produce 1 kHz at its output, pin 3. When the clarifier is on, the 1 kHz at TP3 will vary at least +0.25 kHz with the clarifier control setting. The 1 kHz reference signal to the minor loop is provided by U6, pin 6. U6, pin 3, drives a three section RC filter which converts the square wave at pin 3 into a sine wave at R25. The lower amplifier of U7 is simply a voltage follower used to bias the upper half output at one half of the supply voltage. Pin 1 of U7 provides the 1 kHz tone output. Additional filtering of the signal is provided by C31 and R24. The frequency of the TCXO Y2 can be adjusted by first removing the access screw on the cover. A small screwdriver may then be used to adjust the frequency.
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