User's Manual

3300-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections
335B, Rev. 0 2-3
Channel Oscillator Board
NOTE: If the precise frequency kit is
present in your transmitter, the VCXO
Channel Oscillator Board (1145-1204)
will be used.
The channel oscillator board (1145-1201)
or VCXO board generates a stable
frequency reference signal of
approximately 100 MHz. The output
connects to the x2 multiplier board.
Transmitter Control Board
The (A17) transmitter control board
(1265-1311) provides system control
functions and the operational LED
indications, which can be viewed on the
front panel of the transmitter. The main
control functions are the
Operate/Standby and Auto/Manual
selections. When the transmitter is
switched to Operate, the board supplies
the enables to the three external VHF
amplifier trays. The board also performs
the automatic switching of the
transmitter to Standby upon the loss of
the video input when the transmitter is in
Automatic.
Visual/Aural Metering Board
The (A19) visual/aural metering board
(1265-1309) provides detected outputs
of the visual, aural, and reflected output
samples that are used for monitoring on
the front panel meter. These readings are
attained from the forward power and the
reflected power samples from the output
coupler assembly of the transmitter.
4 Way Power Splitter
The RF output of the VHF exciter is split
four ways in (A5) the 4-way power
splitter assembly (ZFSC-4-3BNC). Only
three of the outputs are used in this
configuration, the fourth is terminated.
VHF Low Band Amplifier Tray
The outputs of the splitter feed the three
(A6, A7 and A11) VHF amplifier trays
(1304363). Each tray amplifies the RF
signals to approximately 750 watts peak
of sync visual + aural.
In the VHF amplifier tray, a forward
power sample and a reflected power
sample from the combiner board are
connected to the AGC control board that
provides peak-detected samples that are
monitored on the front panel meter of
the tray.
3 Way VHF Combiner Assembly
The outputs of the three VHF amplifier
trays are combined in (A8) the 3 way
VHF combiner that provides
approximately 2100 watts peak of sync
output.
Harmonic and Bandpass Filters
The output of the combiner assembly is
connected to (A13) a harmonic filter and
(A14) a bandpass filter assembly. The
harmonic and bandpass filters are tuned
to provide a high out-of-band rejection of
unwanted products.
Output Coupler Assembly
The filtered signal is connected to the
(A16) coupler assembly, which provides
a forward and a reflected power sample
to the visual/aural metering board
mounted 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
visual monitoring of the system
operation.