User's Manual

Digital UHF Transmitter Chapter 4, Circuit Descriptions
DT835A, Rev. 1 4-29
the Amplifier Array contains an External
Exhaust Kit, then a Fan Enable is
supplied at J4-19 with +12V at J4-20
that connect to the fan mounted on the
roof which turns it on..
Main AC Input
Each Amplifier Assembly needs an AC
Input of 208/240 VAC at 100 Amps
Single Phase or 208/240 VAC at 55
Amps Three Phase wired to it. The
208/240 VAC Input to each Amplifier
Assembly connects to (A10) the AC
Distribution Assembly, Amplifier Array
(1278-1200 Single Phase or 1278-1100
Three Phase) located on the right side,
center rear of each Cabinet. Each AC
Distribution Assembly contains the
Terminal Block (TB1) to which the
208/240 VAC connects. For Single
Phase operation connect Line 1 to TB1-
1A, Line 2 to TB1-3A and Ground to
TB1-4A and for Three Phase operation,
connect Line 1 to TB1-1A, Line 2 to
TB1-2A, Line 3 to TB1-3A and Ground
to TB1-4A. The AC Distribution Panel
contains from five to seven Circuit
Breakers that supply the AC to the rest
of the Amplifier Assembly. The Input
AC from TB1 is connected to (CB1) the
Main AC Circuit Breaker (100 Amps for
Single Phase or 80 Amps for Three
Phase) which distributes the 220 VAC
to the other circuit breakers (CB2-
CB7). The CB6 and CB7 Circuit
Breakers are used if the extra Amplifier
Trays are needed. The output of CB1
has three MOVs, VR1, VR2 and VR3 for
Single Phase or six MOVs VR1-VR6 for
Three Phase, mounted to it, one
connected from each leg of the Input
AC to ground and one across the each
of the legs.
The switched Input AC is wired through
a maximum of six Circuit Breakers,
CB2-CB7, to the UHF Amplifier Trays in
the Amplifier Array Cabinets. CB2 is a
20 Amp Circuit Breaker that supplies
the AC voltage to the (A1) UHF
Amplifier Tray. CB3 is a 20 Amp Circuit
Breaker which supplies the AC voltage
to the (A2) UHF Amplifier Tray. CB4 is
a 20 Amp Circuit Breaker which
supplies the AC voltage to the (A3) UHF
Amplifier Tray. CB5 is a 20 Amp Circuit
Breaker which supplies the AC voltage
to the (A4) UHF Amplifier Tray. The
CB6 and CB7 circuit breakers are part
of the (Optional) 2.5 kW or 3 kW High
Power Kit and may not be present.
CB6 is a 20 Amp Circuit Breaker which
supplies the AC voltage to the (A5) UHF
Amplifier Tray. CB7 is a 20 Amp Circuit
Breaker which supplies the AC voltage
to the (A6) UHF Amplifier Tray. In the
(Optional) 2.5 kW and 3 kW Amplifier
Array Assemblies circuit breakers CB8
and CB9 apply AC to the (A12-A3 &
A12-A5) Fans located on (A12) the
Reject Load Assembly.
When the Circuit Breaker CB1 on the
AC Distribution Assembly in the UHF
Exciter Assembly is switched On, +12
VDC from the Exciter is supplied to
each of the Amplifier Array Cabinets.
In the Amplifier Array, the +12 VDC is
split and connected to each of the UHF
Amplifier Trays in the Amplifier
Assemblies for operation of the LED
Status Indicators in the Tray.
4.8 (A1, A2, A3 & A4 with A5 & A6
used in 2.5 & 3 kW Arrays) UHF
Amplifier Trays (1294-1112 low
band/1294-1113 mid band/1294-
1114 high band; Appendix C)
4.8.1 (A1) UHF Filter (1007-1101;
Appendix D)
The UHF filter is a tunable two-section
cavity filter that is typically tuned for a
bandwidth of 6 MHz and has a loss of
-1 dB through the filter.
4.8.2 (A3) 1-Watt Amplifier Board
Assembly (1227-1319; Appendix D)
The 1-watt UHF amplifier board
assembly provides radio frequency
interference (RFI) and electromagnetic
interference (EMI) protection, as well