User's Manual

3300-Watt VHF Low Band Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections
335B, Rev. 0 2-6
Table 2-3. VHF Exciter Tray Switches
SWITCH FUNCTION
S1
Transmitter
Operate/Standby
The momentary switch S1 applies a ground to K1, a latching
relay on the transmitter control board. K1 will switch either
to Operate or to Standby depending on which direction S1 is
pushed. When switched to Operate, the low, Enable
commands are applied to the VHF amplifier trays. These
Enables will turn on the VHF amplifier trays. The opposite
occurs when the switch is turned to Standby.
S2
Mode Select
Auto/Manual
The momentary switch S2 applies a ground to K2, a latching
relay on the transmitter control board. K2 will switch the
transmitter to Automatic or Manual depending on which
direction S2 is pushed. In Automatic, the video fault
command from the ALC Board will control the operation of
the transmitter. The transmitter will switch to Standby, after
a slight delay, if the input video is lost and will switch back to
Operate, quickly, when the video is restored. In Manual, the
transmitter is controlled by the operator using the front panel
Operate/Standby switch or by remote control.
R1
Power Adjust
The 5 kΩ pot (A20) sets the ALC level on the ALC board that
controls the output power of the transmitter.
Table 2-4. VHF Exciter Tray Fault Indicators
INDICATOR DESCRIPTION
DS9
Video Loss
(Red)
Indicates that the input video to the transmitter has been
lost. The fault is generated on the ALC board in the VHF
exciter tray.
DS7
VSWR Cutback
(Amber)
Indicates that the reflected power level of the transmitter has
increased above 20%. This automatically cuts back the
output power level to 20%. The fault is generated on the
transmitter control board in the VHF exciter tray.
Table 2-5. VHF Exciter Tray Samples
SAMPLE DESCRIPTION
f(IF)
A sample of the visual IF that is taken from the sample jack
on the IF carrier oven oscillator board.
f(IC)
A sample of the intercarrier signal that is taken from the
sample jack on the aural IF synthesizer board.
f(s)
A sample of the channel oscillator output that is taken from
the sample jack of the channel oscillator assembly.
Exciter O/P
An output power sample of the exciter that is taken from the
VHF filter/amplifier board.
Transmitter O/P
A forward power sample of the transmitter that is taken from
the output coupler assembly through the visual/aural
metering board.