Remote Control/Monitor Interface (A5PC1J5)
Jack – Pin #
Function
2
6
15
J5 – 6
REMOTE AGC ON/OFF: By applying a ground, this pin can be used to deacti-
vate the output AGC voltage that controls IF/Converter PIN diode attenuator
PC1CR9/CR10. In the TTU500FA, the same result is achieved by placing a
ground on pin 7 of jack A8J1 on the rear Video/Audio/Remote panel. This low
will be passed on to A5PC1J4-7, looped through A5PC1J5-6 and sent to J5-6.
The low now found at U4D-12 will force U4D-8 and J8-10 low forcing PIN diodes
PC1CR9/CR10 to stabilize at the center of their attenuation range (
3dB).
Whether the output of AND gate U4C is at a logic high or low, that signal is also
sent to pin 18 of J10 through resistor R23 and on to front panel AGC ACTIVE
LED P3DS6. If the voltage is high, transistor PC3Q6 will be forward biased
causing the LED to turn on, indicating the output AGC is active. If the voltage
at PC3J1-18 is low, PC3Q6 will not conduct and PC3DS6 will not illuminate
indicating an inactive output AGC.
J5 – 7
FWD PWR IN: The incoming voltage at this pin is proportional to the forward
output power of the transmitter and is forwarded to pin 3 of buffer U7A from
Metering Detector A7A1J3-5 via A5PC1J6-5, buffer amplifier A5PC1U4A and
A5PC1J5-7. When this voltage is available, the Exciter is driving higher power
equipment and pins 1 & 3 of jumper JP1 are closed sending the metering voltage
from U7A to the front panel AGC ADJUST amplifier PC3U1 through J10-19 and
PC3J1-19. From AGC ADJUST PC3R15, this PWR REFERENCE signal
reaches PC1J6-8 of the IF/Converter by PC3J1-17, J10-17 and J8-8. This
voltage acts as the reference for the IF/Converter’s output AGC loop by
controlling variable attenuator PC1CR9/CR10 and compensating for any power
variations occurring at the transmitter’s output. If for some reason the transmit-
ter’s output power were to drop, the positive voltage at J8-8 would be reduced.
The change in level reduces the attenuation provided by PIN diodes PC1CR9/
CR10 in proportion to the power decrease seen at the transmitter’s output,
thereby bringing the transmitter’s power back to its appropriate operating level.
In the case where the transmitter’s output increases above its rated output, the
PWR REFERENCE voltage at J8-8 will increase causing attenuator PC1CR9/
CR10 to increase resistance, decreasing the transmitter’s output signal level to
its proper value.
J5 – 8
GND: Ground provided to the operator’s remote equipment from the Exciter or
to the TTU500FA Video/Audio/Remote rear panel jack A8J1-8 via A5PC1J4-8
and A5PC1J5-8.
Transmitter Control/Monitor Interface (A5PC1J3)
Jack – Pin #
Function
J4 – 1
AMP STATUS IN: In the TTU500FA, a power supply failure, overtemperature
condition or transistor failure occurring in the 500W UHF Power Amplifier drawer
(A3) will furnish a low to this pin from A5PC1J3-1. The resulting lows at U4A-3,
U4D-11 and U4C-8 are sent through J8-10 to IF/Converter switch PC1S2 which
determines if the IF output AGC is active (high) or fixed (low). With a low at
PC1S2-6, pins 1 & 2, 3 are closed placing a ground on PC1U18-3. This low
forces PIN diodes PC1CR9/CR10 to stabilize at the center of their attenuation
