Data Sheet Chapter 5

10-kW UHF Transmitter with Chapter 5, Detailed Alignment Procedures
Feedforward Drive
840A, Rev. 0 5-2
5.1.2 (A24) (Optional) Composite
4.5-MHz Filter Board (1227-1244;
Appendix B)
The (A24) (optional) composite 4.5-MHz
filter board will only function properly
with a 4.5-MHz composite input signal
and with the 4.5-MHz composite input
selected.
Connect the test signal from an envelope
delay measurement set to the video
input of the tray at J1 or J2.
Connect an oscilloscope to jack J7, video
out, between the J7 center pin and pin 1
or 3 ground. Adjust C21, frequency
response, if needed, for the best
frequency response. Adjust R32, video
gain, for a signal level of 1 Vpk-pk on the
oscilloscope.
The output at J6 and J7 of the board
should be video only with no 4.5-MHz
aural subcarrier.
5.1.3 (A25) (Optional) 4.5-MHz
Bandpass Filter Board (1265-1307;
Appendix B)
The (A25) (optional) 4.5-MHz bandpass
filter board will only function properly
with a 4.5-MHz composite input signal
and with the 4.5-MHz composite input
selected.
Adjust the filter with L2, C3, L4, and C7
for a frequency response of no greater
than ±.3 dB from 4.4 to 4.6 MHz.
Adjust C19 for an overall peak-to-peak
variation of less than ±.3 dB from 4.4
MHz to 4.6 MHz.
Recheck the frequency response; it may
have changed with the adjustment of the
envelope delay. If necessary, retune the
board.
5.1.4 (A7) IF Carrier Oscillator Board
(1191-1404; Appendix B)
To align (A7) the IF carrier oscillator
board:
1. While monitoring J3 with a
spectrum analyzer, observe the
45.75-MHz visual IF (typical +5
dBm).
2. Connect a frequency counter to J3
and adjust C17 for 45.750000 MHz.
3. Connect a frequency counter to J1
and check for 50 kHz; this is the
aural phase lock loop (PLL)
reference.
5.1.5 (A5) Sync Tip Clamp/
Modulator Board (1265-1302;
Appendix B)
To align (A5) the sync tip clamp/
modulator board:
1. Determine if jumper W4 on jack J3
is present. Jumper W4 terminates
the video input into 75Ω. Remove
jumper W4 if the video loop-
through is required on the rear
chassis at jacks J1 and J2.
2. Set the controls R20, the white clip,
R24, the sync clip, and R45, the
sync stretch cut-in, to their fully
counter-clockwise (CCW) position.
Set R48, the sync magnitude, fully
clockwise (CW).
3. Place the jumper W7 on jack J4 to
the clamp off, disable, position.
4. Connect a 5-step staircase video
test signal to the input of the
transmitter.
5. Monitor TP2 with an oscilloscope.
Adjust R12, the video gain pot, for
1 Vpk-pk.
6. Change the video input test signal
to a multiburst test pattern. While