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5.9.13 COUPLER INTERFACE BOARD, 1A19
See Figure 5.56 for the schematic of the Coupler Interface board.
This board acts as an interface for inputs and outputs between the Controller board, Interface board, Auxiliary connector, Accessory connector, and the signal path boards. The two basic functions performed by this board are: control of transmitter keying and control of a system antenna coupler. See Figure 4.5 for a simplified diagram of the keying circuits.
5.9.13.1 Keying Inputs and Outputs
Following is a listing of the various keying inputs and use restrictions.
1. Pin20 - / T0NE KEY. A logic low at this input will key the transmitter under all conditions. This pin is connected to the TONE KEY output of the optional Tone Key Modem board.
2. Pin 16 - /EXT KEY. This input from the rear panel will also key the transmitter whenever it is pulled low.
3. Pin 18 - /FSK KEY. This input from the rear panel will key the transmitter when pulled low only if the radio is in the FSK mode.
4. Pin14-/PTT. This is another front panel input which keys the transmitter in any mode unless Pin32, REM, is a logic high.
5. Pin32-REM. This input is high whenever the radio is being remotely controlled, In this state, the /CW KEY and /PTT are both disabled.
6. Pin 22 -1iP KEY. This signal comes directly from the microprocessor and keys the transmitter whenever it is a logic high.
7. Pin 8 -/KEY ENABLE. This comes from the system antenna coupler and keys the transmitter during a coupler TUNE cycle. A logic low at this input will key the transmitter only when a TUNE cycle is commanded by a logic high at Pin 33, TUNE B.
The following pins are transmitter keying outputs:
1. Pin25-/TX1. This is the primary keying output which sets all signal path boards in the transmit mode. This output also controls the front panel TX LED. This output goes low when the transmitter is keyed.
2. Pin 36 - /TX2. This output is similar to /TX1 except that it is used to key external equipment by going low when the transmitter is keyed.
3. Pin 37-/TX3. This output is similar to/TX-I and/TX2 except it is not disabled by the TX INHIBIT circuitry. /TX3 is used to control the MSR 4030coupler bypass circuitry, disabling the bypass relay whenever the transmitter is keyed. /TX3also informs the u-P when there is any attempt to key the transmitter.
4. Pin 24 - /AUDIO KEY. This output differs from TX1 in that it is not affected by the CW delay,
It controls the transmitter modulation in CW mode.
5. Pin17-/AMT. This output is logic low when the transmitter is keyed in AME mode.
The following inputs all inhibit the transmitter keying. When active, the TX INHIBIT LED will light and the test point (TP11hrough TP4) responsible for the inhibit will be a logic low.
1. Pin 11 - KEY INTERLOCK. This input is used by the antenna coupler to ensure that the transmitter will not be keyed at a time when the coupler is vulnerable to damage.
This line must be pulled low or the transmitter cannot be keyed, If an antenna coupler is NOT in the system, a shorting plug connecting this pin to ground must be Connected to the radio's accessory connector (Pin 11to ground in the accessory connector). This function may also be controlled on J36 pin 4 if Motherboard jumper JP4 is in position 2-3.
2. Pin 38 - /LL. This input goes to a logic low whenever any of the loops in the synthesizer loses lock. This prevents transmitter keying Unless the frequency is valid.
3. Pin 29 - /TX INHIBIT. This is used by the microprocessor to prevent keying at any time that the software program has determined that keying is inappropriate, such as during a mode change or during Silent Tune.4. Pin 34-/ PSFAULT. This input comes from the power supply and prevents keying whenever the power supply is disabled.
5.9.13.2 Keying control circuits
When any of the keying inputs (except for the coupler /KEY ENABLE) commands the transmitter to key and no inhibiting signals exist, U1 pin 8will be high. This brings the /AUDIO KEY line to a logic low. U1 OA provides a variable CW "hang" delay when the radio is in CW mode. A high at U3pin 2 lengthens the key down time in CW mode.
Keying can be prevented by a high at U3 pin 11 or
U6 pin 6. U3 pin11 is high during a coupler TUNE cycle and U6 pin 6 is high if any of the inhibit inputs is active, If neither of these points is high, a keying input will cause /TX1, /TX2 and /TX3 to go to a logic low. Note that /TX3 is not affected by the transmit inhibit signals. /TX3 does not key the transmitter; it is used to turn off the MSR 4030coupler bypass relay during transmit mode.
5.9.13.3 coupler control circuit
Inverter/ drivers U13A, U12C, U14D, U14C and U14B interpret coupler control inputs.
The /TUNING line is taken to a logic low by the coupler whenever the antenna coupler is tuning. If switch 81-3 is closed, the tuning "BEEP" is energized. This commands the radio to create a pulsing audio tone audible in the speaker during the TUNE cycle.
VSWR RETUNE is an optional coupler feature which provides for an automatic coupler TUNE whenever a VSWR FAULT is detected by the antenna coupler or the linear power amplifier (if used). A TUNE cycle is requested by the coupler or LPA by pulling the /TUNING input low (when not already in a TUNE cycle). U10B prolongs the duration of this momentary low-going pulse, so that it will be detected by the microprocessor, If the VSWR RETUNE is not desired. S1-2 is left open, deactivating U10B. NOTE: Selection of the VSWR RETUNE feature also requires the closure of the VSWR RETUNE coupler option switch located elsewhere in the radio.
Coupler TUNE commands from the microprocessor are on TUNE B (Pin 33) for normal tune and SILENT B (Pin 26) for a silent tune (MSR 4030only). These commands are inverted by U8D andU8E and are denoted as /TUNE and /SIL TUNE.
U15 and K1 prevent the coupler tune commands from being sent to the coupler before the radio has been turned on long enough to clear any transient.
When a coupler TUNE is commanded (Pin 33 high), U3 pin 11 will be high, disabling all keying inputs except the coupler keying input /KEY ENABLE. The coupler pulls this line low when it needs an rf signal to operate during the TUNE cycle.
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