User's Manual

Digital UHF Transmitter Chapter 2, System Description and
Customer Remote Connections
DT835A, Rev. 1 2-5
2.1.8 UHF Exciter Tray
Table 2-3: UHF Exciter Tray Meters
METER FUNCTION
Meter (A18) Displays power in terms of a percentage of the calibrated
exciter output level on the upper scale. The voltage level is
read on one of the two bottom scales. A full-scale reading on
the top scale is 120%. 100% equals +10 dBm 8-VSB digital.
Also reads the ALC voltage level.
Switch (S3), meter Selects the desired % Exciter or the ALC voltage reading
ALC (0 - 1 V) Displays the ALC voltage level (≈0.85 VDC)
% Exciter Displays the % Exciter Output Power. This is the level needed
to attain (0 -100) which is the desired output power of the
transmitter (≈ 30 %).
Table 2-4: UHF Exciter Tray Switches
SWITCH FUNCTION
Transmitter (S1)
Operate/Standby
The momentary contact 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, a low, Enable
command, is applied to the UHF amplifier trays mounted in the
amplifier arrays. These Enables will turn on the UHF amplifier
trays. The opposite occurs when the transmitter is switched to
Standby.
Mode Select (S2)
Auto/Manual
The momentary contact 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 Modulation 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 modulation is lost and will quickly
switch back to Operate when the modulation is restored. In
Manual, the transmitter is controlled by the operator using the
front panel Operate/Standby switch or by remote control.
Table 2-5: UHF Exciter Tray Fault Indicators
FAULT INDICATOR FUNCTION
Modulation loss (DS9
red)
Indicates that the input has been lost to the transmitter. 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 transmitter
has increased above 20%. This will automatically cut back
the output power level to 20%. The fault is generated on the
transmitter control board in the UHF exciter tray.