User's Manual

2650 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures
435B, Rev. 0 3-6
and operation procedures that follow
before applying power to the transmitter.
3.4 Setup and Operation
Initially, the transmitter should be turned
on with the RF output at (A9-A5-J2) the
bandpass filter assembly terminated into
a dummy load of at least 2650 watts. If a
load is not available, check that the
output of the bandpass filter assembly is
connected to the antenna.
Connect the baseband balanced audio
input to the terminal block TB1 or the
composite audio input to BNC jack J6 on
the A/V input & remote interface
assembly, located facing the rear of the
cabinet near the top. The baseband
audio input can remain connected when
using the 4.5 MHz composite input
without affecting the operation of the
transmitter. Connect the baseband video
input to BNC jack J2 also on the A/V I/P
& remote interface assembly, if the
(optional) 4.5 MHz composite input kit is
purchased, connect the 4.5-MHz
composite input to the BNC jack J2. To
use the 4.5 MHz composite input, the 4.5
MHz composite input must be connected
to J2 and the baseband select must be
removed from J7-6 and J7-7 on the rear
of the VHF Exciter tray. To use the
baseband video and audio inputs, the
baseband video input must be connected
to J2, the baseband audio must be
connected to the proper jack, and the
baseband select must be connected from
J7-6 and J7-7.
Switch on the main AC, VHF exciter, and
the amplifier #1 and amplifier #2 circuit
breakers on the AC distribution panel
facing the rear of the cabinet and
mounted behind the rear door. On the
VHF exciter tray, switch the
Operate/Standby switch to Standby and
the Auto/Manual switch to Manual.
NOTE: Normal operation of the
transmitter is in Automatic. Automatic
operation uses the video input to the VHF
exciter as an Operate/Standby switch. In
Auto, if the input video is lost for
approximately 7 seconds, the transmitter
will automatically revert to Standby and,
when the video signal is restored, the
transmitter will quickly return to Operate.
Move the Operate/Standby switch on the
VHF exciter tray to Operate. Observe the
power supply reading, +28 V, on the
front panel of the VHF amplifier trays.
Note: If the transmitter does not switch
to Operate when the Operate/Standby
switch is placed in Operate, check that an
external interlock plug, with a jumper
wired from pins 21 to 22, is connected to
jack J9 on the (A12) A/V input and
remote interface assembly.
On the VHF exciter tray, look at the front
panel meter reading in the % Visual
Power position; it should read 100%. If
necessary, readjust the screwdriver
adjust power pot on the front panel of
the VHF exciter for 100%. As the power
level is being checked, observe the meter
reading in the % Reflected Power
position. If the % Reflected Power is
very high, above 10%, a problem exists
with the output coaxial lines and they will
need to be checked. A center bullet
missing from the 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 VHF amplifier
trays were adjusted at the factory to
obtain an output of 100% for the
transmitter and should not need to be
readjusted. The front panel readings on
the individual VHF amplifier trays may
not be the same. Refer to the Test Data
Sheet for the transmitter to compare the
final readings from the factory with the
readings on each of the trays after the
setup. They should be very similar. If a
reading is off by a significant amount,
refer to the phasing and power
adjustment procedures for the VHF
amplifier trays in Chapter 5, Detailed
Alignment Procedures, of this manual
before trying to make any adjustments.