System Description Chapter 2

10-kW UHF Transmitter with Chapter 2, System Description
Feedforward Driver
840A, Rev. 0 2-5
Table 2-3. UHF Exciter Tray Control Switches
SWITCH FUNCTION
Transmitter (S1)
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 four UHF
amplifier trays. The opposite occurs when
S1 is switched to Standby.
Mode Select (S2)
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 video input 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.
Power Adjust (R1)
The 5 kΩ pot, A20, sets the ALC level on
the ALC board. This sets the output power
for the transmitter.
Table 2-4. UHF Exciter Tray Fault Indicators
FAULT INDICATOR FUNCTION
Video Loss (DS9 Red)
Indicates that the video input to the
transmitter has been lost. The fault is
generated on the ALC board in the UHF
exciter tray.
VSWR Cutback (DS7 Amber)
Indicates that the reflected power level of
the 10-kW transmitter has increased above
15%. This will automatically cut back the
output power level to 15%. The fault is
generated on the transmitter control board
in the UHF exciter tray and is derived from
a peak-detected voltage in the amplifier
cabinet.