Assembly Instructions Chapter 3

3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures
835-3, Rev. 0 3-6
3.5 Operation and Setup Procedures
Initially, the transmitter should be turned on with the RF output at J2 of (A11) the
output coupler assembly terminated into a dummy load of at least 3000 watts. If a load
is not available, check that the output of the coupler assembly is connected to the
antenna.
Connect the baseband, balanced audio input to XLR jack J5 or the composite audio,
stereo, input to BNC jack J3 on the rear of the top UHF exciter tray for the 3-kW
transmitter. Connect the baseband video input to BNC jack J1 also on the rear of the
UHF exciter assembly.
Switch on the main AC and UHF exciter circuit breakers on the AC distribution panel in
the exciter cabinet. Switch on the main AC and all of the amplifier circuit breakers on
the AC distribution panel in the amplifier array cabinet. Also switch on the circuit
breaker on the rear of the UHF exciter tray for the 3-kW transmitter. Move the
Operate/Standby switch on the front panel of the UHF exciter to Standby and move the
Auto/Manual switch to Manual. Normal operation of the transmitter is with the
Auto/Manual switch in Automatic. Automatic operation of the transmitter uses the video
input to the UHF exciter as an Operate/Standby switch. In Auto, if the input video is
lost, the transmitter will automatically revert to Standby and, when the video signal is
restored, the transmitter will automatically return to Operate.
Move the Operate/Standby switch on the UHF exciter tray to Operate. Note the power
supply reading, +28 VDC, on the front panel of each of the 600-watt amplifier trays.
Note: If the transmitter does not switch to Operate when the Operate/Standby
switch is moved to Operate, check that the external interlock plug, with a
jumper from pins 23 to 24, is connected to jack J11 on the rear of the UHF
exciter tray.
Observe the % Output Power reading of the meter on the UHF exciter tray; it should
read 100%. If needed, adjust the power adjust screwdriver adjust pot on the front panel
of the UHF exciter. As the power level is being observed, check the meter reading in the
% Reflected Power position. If the % Reflected Power is very high, above 40%, there
may be a problem with the output coaxial lines that needs to be checked and corrected.
A center bullet missing from the 7/8-inch or 3 1/8-inch rigid coax lines or loose bolts on
the connections can cause this problem. Return the Operate/Standby switch to Standby.
The gain and phase controls on the front panels of the individual 600-watt UHF amplifier
trays need to be adjusted to attain 100% output of the transmitter. The readings on the
individual trays may not all be the same. To set up the phasing and power adjustment
procedure for the 600-watt amplifier trays, refer to Section 4, Detailed Alignment
Procedures, of this manual.
If a dummy load is connected to the transmitter, switch the transmitter to Standby and
switch off the AC circuit breaker on the rear of the UHF exciter tray. Also switch off the
main AC circuit breaker for the amplifier array cabinet. Remove the dummy load and
make all of the connections required to hook up the transmitter to the antenna. Switch
on the UHF exciter and the amplifier array main AC circuit breaker. Move the
Operate/Standby switch to Operate. Adjust the output power screwdriver pot to attain
100% output.
If the transmitter is already connected to the antenna, check that the output is 100%. If
needed, adjust the power screwdriver pot.