User's Manual

Digital UHF Transmitter Chapter 3, Installation and Setup Procedures
DT835A, Rev. 1 3-7
Table 3-2: Jumper Positions in the Gain 1 and Gain 2 Circuits for an
Input Level of Between –6 and –26 dBm
IF Input Range W3 on J4 and W4 on J5 W5 on J6 and W6 on J7
-11 to -6 dBm Low Low
-16 to -11 dBm Low High
-21 to -16 dBm High Low
-26 to -21 dBm High High
3.6 Setup and Operation Procedures
The transmitter should initially be turned
on with the RF output at J2 of the (A11)
output coupler assembly terminated into
a dummy load. If a load is not available,
check that the output of the coupler
assembly at J2 is connected to the
antenna. Connect the digital IF input to
J6 on the rear of the UHF exciter tray. On
(A5) the 5 Section delay equalizer board,
44 MHz, set the input matching jumpers
J2 and J3 to positions 1 and 2 for a 50Ω
input, or to positions 2 and 3 for a 75Ω
input, as needed. Depending on the input
level, two gain circuits on the delay
equalizer board, 44 MHz, are adjusted
using jumpers, W3-W6, to set the gain
through the board. Table 3-2 shows the
jumper positions in the gain 1 and gain 2
circuits for an input level of between -6
to -26 dBm.
Switch on the main AC circuit breaker on
the AC distribution assembly mounted
toward the rear of the single UHF exciter
assembly. Switch on the main AC circuit
breakers on the AC distribution
assemblies mounted toward the rear of
the amplifier cabinets. Switch on the
CB2-CB6 circuit breakers for the
individual UHF amplifier trays on the AC
distribution assemblies mounted in each
amplifier array cabinet.
Switch the Operate/Standby switch on
the UHF exciter to standby and the
Auto/Manual switch, also on the UHF
exciter, to Auto. Normal operation of the
transmitter is with the switch in
Automatic. Automatic operation of the
exciter uses the digital input to the
exciter as an Operate/Standby switch. In
Auto, if the input is lost, the exciter will
automatically cause the transmitter to
revert to Standby. When the input signal
is restored, the exciter will automatically
return the transmitter to Operate.
Move the Operate/Standby switch on the
exciter to Operate. Observe the power
supply readings on the front panel
meters of the UHF amplifier trays in each
amplifier cabinet assembly; the reading
should be +26.5 VDC.
Note: If the transmitter does not
switch to Operate when the
Operate/Standby switch is switched
to Operate, check that there is an
external interlock plug connected to
jack (J7) on the remote interface
assembly mounted in the top, rear of
the single UHF exciter cabinet. Make
sure that the plug has a jumper from
pins 1 to 2 to provide the interlock
for the exciter. The interlock must be
present for the transmitter to
operate.
Observe the front panel meter on the
metering panel with the switch in the
Combined Visual Output Power position;
it should read 100%. If needed, adjust
the power adjust screwdriver pot on the
front panel of the UHF exciter to attain a
100% reading on the front panel meter.
At the same time that the output power
is being observed, check the meter
readings on the metering panel and the
combined meter, in the % Reflected
Power position, for the side A and side B
amplifier assemblies. If the % Reflected
Power for any of the readings is very
high, above 50%, a problem is present
with the output coaxial lines in the side A
amplifier assembly or in the output lines