Data Sheet Chapter 5

4-6 kW UHF Translator Chapter 5, Detailed Alignment Procedures
837B, Rev. 0 5-5
The Receiver Tray is now set up and
ready for normal operation.
5.1 UHF Exciter Tray with Baseband
Video and Audio Inputs (Must have
Optional Modulator Kit.)(1142458 or
1245-1100; Appendix C)
This tray has adjustments for video
levels, audio modulation levels, and other
related parameters.
Connect an NTSC baseband video test
signal input (1 Vpk-pk) to the translator
video input jacks J2 or J1 on the rear of
the tray. Jacks J1 and J2 are loop-
through connected; the unused jack can
be used as a video source for another
transmitter by removing jumper W4 on
jack J3 on (A5) the sync tip clamp/
modulator board (1265-1302). Connect a
baseband audio input (+10 dBm) to the
balanced audio input terminal block TB1-
1 [+], TB1-2 [-], and TB1-3 [ground] or,
if stereo/composite audio is provided,
connect it to BNC jack J3 or J13, the
composite audio input jack. Jacks J3 and
J13 are loop-through connected; the
unused jack can be used as an audio
source for another transmitter by
removing jumper W1 on jack J15 on the
aural IF synthesizer.
Select the baseband input operation by
applying a baseband select, using a
jumper or closed contacts, connected
between J7-6 and J7-7 on the rear of the
tray. Look at the front panel meter on
the UHF exciter tray. In the video
position, the meter indicates active video
from 0 to 1 Vpk-pk. The normal video
input level is 1 Vpk-pk on the meter. If
this reading is not at the proper level, the
overall video level can be changed by
adjusting video level control R12 on (A5)
the sync tip clamp/modulator board
(1265-1302).
Switch the meter to the audio position
that indicates the audio deviation
(modulation level) of the signal from 0 to
100 kHz. The aural IF synthesizer board
was factory set for a ±25-kHz deviation
with a balanced audio input of +10 dBm.
If the reading is not at the correct level,
adjust balanced audio gain pot R13 on
the aural IF synthesizer board, as
necessary, to attain the ±25-kHz
deviation. The aural IF synthesizer board
was factory set for a ±75-kHz deviation
with a composite audio input of 1 Vpk-
pk. If this reading is not correct, adjust
composite audio gain pot R17 on the
aural IF synthesizer board, as necessary,
for the ±75-kHz deviation.
5.2 UHF Exciter Tray with (Optional)
4.5-MHz Composite Input Kit
With the (Optional) 4.5-MHz composite
input kit, the UHF exciter can operate
using either the separate video and audio
baseband inputs or the single 4.5-MHz
composite input. The 4.5-MHz composite
input kit includes a composite (A24) 4.5-
MHz filter board and (A25) a 4.5-MHz
bandpass filter board.
To operate the transmitter using the 4.5-
MHz composite input, remove the
baseband select command from J7-6 and
J7-7 on the rear of the tray.
Connect a multiburst test signal from an
envelope delay measurement, set to the
input of the tray, at J1 or J2. On (A24)
the composite 4.5-MHz filter board,
connect an oscilloscope between J7, the
center pin, and pin 1 or 3, which are
ground. If necessary, adjust C21 for the
best frequency response. Adjust R32 for
a signal level of 1 Vpk-pk on the
oscilloscope. The output, as measured at
J6 and J7 of the board, should be video
only, with a minimum 4.5-MHz aural
subcarrier.
On (A25) the 4.5-MHz bandpass filter
board, 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