User's Manual

2650 Watt VHF High Band Transmitter Chapter 2, System Description,
Maintenance and Remote Interface Connections
435B, Rev. 0 2-1
Chapter 2
System Description, Maintenance
and Remote Interface Connections
The 435B is a complete 2650 watt VHF
high band solid state internally diplexed
television transmitter that operates at a
nominal visual output power of 2650
watts peak sync and an average aural
output power of 265 watts, at an A/V
ratio of 10 dB, 10% sound, or 132.5
watts at 13 dB, 5% sound.
2.1 System Overview
The 435B is made up of the trays and
assemblies listed in Table 2-1.
Table 2-1. 435B Major Trays and Assemblies
MAJOR ASSEMBLY
DESIGNATOR
TRAY/ASSEMBLY NAME DRAWING NUMBER
A2 AC distribution panel 1265-1600
A4 VHF exciter 1070901
A6, A7, A13, A14 Four VHF amplifier trays 1301169
A8 VHF combiner assembly 1219-1006
A12 Remote interface assembly 1083510
The (A4) VHF exciter can operate using
either the baseband audio and video
inputs alone or, if the (optional) 4.5-MHz
composite input kit is purchased, the 4.5-
MHz composite input or the baseband
video and audio inputs to produce a
diplexed, modulated, and on-channel
frequency visual + aural RF output. The
switching is accomplished by a relay on
the sync tip clamp modulator board that
uses a baseband select to control a relay
that selects either the 4.5 MHz generated
from the baseband inputs or from the
4.5-MHz composite input.
To operate the transmitter with the
(optional) 4.5-MHz composite input kit
using baseband inputs, the baseband
video must be connected to J1 or J2, the
baseband audio must be connected to
the proper input jack, and a baseband
select must be connected from J7-6 and
J7-7. To operate the transmitter with the
(optional) 4.5-MHz composite input kit
using the 4.5-MHz composite input, the
4.5-MHz composite input must be
connected to J1 or J2 and the baseband
select must be removed from J7-6 and
J7-7.
The RF output of the VHF exciter is split
four ways in (A5) the 4-way power
splitter assembly. The outputs of the
splitter feed the four (A6,A7,A13,A14)
VHF high band amplifier trays that
amplify the RF signals to approximately
750 watts pk. of sync each. The outputs
of the four VHF amplifier trays are
combined in (A8) a VHF combiner
assembly that provides approximately
2650 watts peak of sync output. The
2650 watt output is connected to (A9) a
bandpass filter assembly. The bandpass
filter is tuned to provide the high out-of-
band rejection of unwanted products. The
filter assembly provides a forward and a
reflected power sample to the
visual/aural metering board in the VHF
exciter. The forward sample is processed
to provide peak detected visual and aural
power output samples to the transmitter
control board in the VHF exciter. The
reflected power sample is also peak
detected and wired to the transmitter
control board. The transmitter control
board connects the visual, aural, and
reflected power output samples to the
front panel meter for monitoring the
system.