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Exciter Remote Interface (A2J5)
Jack – Pin #
Function
J5 – 1
REMOTE OP/STBY: This control pin is looped through J4-5 and connected to
pin 5 of REMOTE plug A8J1 to remotely control the operate/standby function of
the transmitter. See the function description of J4-5 above for further
information.
J5 – 3
REFLECTED POWER: This voltage, brought into the Control/Monitor board
from Metering Detector A7A1J3-1 via J6-1 and buffered by U4B, is proportional
to any reflected power present at the transmitter’s output. Sent from J5-3 to
A2PC4J5-3, this voltage is monitored by comparator A2PC4U6A for an exces-
sive returned power indication at pin 3 which could exceed the reference at pin 2,
a level determined by VSWR OVLD REF potentiometer A2PC4R12 (25% of the
transmitter’s forward rating). With high VSWR, output pin A2PC4U6A-1 will turn
positive causing output pins 5 & 6 of flip-flop A2PC4U9A to change polarity. As
A2PC4U9A-5 goes negative, gate A2PC4U2D will output a low on pin 11 sending
A2PC4U2A-3 and A2PC4U8A-1 low. The low at A2PC4J10-2 proceeds to
A2PC3J1-21, LEVEL ADJUST A2PC3R16, A2PC3J1-23, A2PC4J10-23,
A2PC4J8-7 and A2PC1-7, causing buffer A2PC1U9 to set IF input attenuator
A2PC1CR7/CR8 at maximum attenuation. This action reduces the output power
of the Exciter and transmitter approximately 50B to insure that no amplifier
damage occurs due to excessive output VSWR. Concurrently, the high
generated at A2PC4U9A-6 is used to light VSWR OVERLOAD indicator
A2PC3DS8 via A2PC4J10-11, A2PC3J1-11 and transistor A2PC3Q8.
J5 – 4
AGC VOLTAGE: This is the same voltage that drives the AGC meter
(A2PC3DS12) located on the front panel of the Exciter drawer. This voltage is
a representation of the IF/Converter output AGC voltage taken from Control/
Interface amplifier A2PC4U8B and made available for monitoring at REMOTE
jack A8J1-2 via A2PC4J5-4, J5-4 and J4-2.
J5 – 6
REMOTE AGC ON/OFF: This control begins at REMOTE jack A8J1-7 and, by
applying a ground to this pin, the voltage that controls IF/Converter output AGC
attenuator A2PC1CR9/CR10 will be deactivated. This ground will be looped
through J5-6 from J4-7 and sent to A2PC4J5-6. The low now found at gate
A2PC4U4D-12 will shift A2PC4U4C-8 and A2PC4J8-10 low, forcing IF/Converter
PIN diodes A2PC1CR9/CR10 to stabilize at the center of their attenuation range
(
3dB). With the output of A2PC4U4C at a logic low, that signal is also sent to
pin A2PC4J10-18 and on to front panel AGC ACTIVE LED A2PC3DS6. Since
the voltage at A2PC3J1-18 is low, A2PC3Q6 will not conduct and A2PC3DS6 will
not illuminate indicating an inactive output AGC.
J5 – 5
REMOTE VSWR RESET: This control originates at REMOTE jack A8J1-6,
loops through from J4-6 to the Exciter Control/Interface input A2PC4J5-5 and on
to VSWR overload flip-flop reset pin A2PC4U9A-4. A momentary ground would
normally be applied to this line to bring the transmitter out of standby due to a
VSWR overload created by excessive returned power at the output of the unit.
(A momentary ground is also provided by Exciter front panel VSWR RESET
switch A2PC3S3). The transition from high to low on pin 4 of flip-flop
A2PC4U9A will reset pins 5 & 6 to their original Q (high) and Q NOT (low) states,
removing the low from A2PC4U2D-13 and the high from VSWR OVERLOAD
LED control transistor A2PC3Q8, respectively. Exciter front panel LED
