User's Manual

Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures
DT835A, Rev. 1 5-3
receiver tray is present in the system.
DS5 is always on with no receiver.
The ALC is muted when the transmitter is
in Standby. To monitor the ALC, turn off
the four amplifier on/off circuit breakers
on the AC input assembly in the rear of
the cabinet and switch the transmitter to
Operate. Adjust the power adjust gain
pot on the front panel of the UHF exciter
tray to obtain +0.8 VDC on the front
panel meter in the ALC position. On the
ALC board (1265-1305), move the
jumper W3 on J6 to the Manual position,
between pins 2 and 3, and adjust R87 on
the ALC board for +0.8 VDC on the front
panel meter in the ALC position. Move
the jumper W3 back to Auto, between
pins 1 and 2, which is the normal
operating position. The detected IF signal
level at J19-2 of the ALC board is
connected to the transmitter control
board. This board distributes the level to
the amplifier arrays where it is used as a
reference for the automatic gain control
(AGC) in each amplifier tray.
5.2.1 Delay Equalization Adjustment
The procedure for performing a delay
equalization adjustment for the UHF
exciter tray is described in the following
steps:
1. Set J19 to the proper position (for
either a 50-Ω or 75-Ω input) and
monitor the output of the board at
J10 with a spectrum analyzer.
2. Bypass all attenuation and
equalizer sections, except delay
equalizer #1. With W12 removed,
tune L30 for the proper center
frequency as shown in Table 5-2.
Install W12 on J22 and adjust L21
and C43 for the best frequency
response across the band. Jumper
in attenuator equalizer #1.
3. Pull W14 from J26 and adjust L29
for the proper center frequency.
Install W14 and adjust L18 for the
best frequency response.
4. Repeat Steps 2 and 3 for each
delay/attenuation equalizer while
tuning the proper inductor for
each section.
5. After all five delay/attenuation
equalizers have been adjusted
according to Table 5-4,
individually jumper in all of the
sections and fine tune, as needed,
for the best group delay and
frequency response.
Table 5-4: Center Frequencies for the Delay Equalizer Sections
DELAY EQUALIZER SECTION CENTER FREQUENCY
1 46.5 MHz
2 44 MHz
3 44 MHz
4 41.5 MHz
5 44 MHz