User's Manual

Digital UHF Transmitter Chapter 4, Circuit Descriptions
DT835A, Rev. 1 4-24
panel mounted ALC adjust Pot (A8)
connects through (A5) the Metering
Board (1245-1202) to J5 on the Board
which controls the output level to the
tray. A front panel mounted Phase
adjust Pot (A7) connects through the
Metering Board to J4 on the Variable
Phase/Gain Board which controls the
phasing of the RF output. The Phasing
adjust is needed to phase the two RF
outputs of the Amplifier Arrays, when
they are combined, to achieve
maximum output. The phase and level
controlled RF signal connects to J2 of
the Variable Phase/Gain Board which
connects to the RF Output Jack J3
located on the rear panel of the Tray.
A sample of the RF from the Variable
Phase/Gain Board connects to J4 the
output Sample Jack located on the
front panel of the Tray.
4.4.2 (A5) Metering Board (1245-
1202; Appendix D)
A detected output sample level
connects to the Metering Board at J7
Pins 3 & 4 which is connected to the %
Power Level position on (A6) the front
panel meter of the Tray. S1 is a two
position front panel mounted switch
that allows the operator to view the
ALC Level, typically reads .6V - 1V, or
the % Power, which is calibrated for
100 % is +23 dBm output.
4.4.3 (A1) Power Entry Module
Assembly (1227-1206; Appendix
D)
120/240 VAC connects to the Tray at J2
on (A1) the Power Entry Module
Assembly. Jumpers on the Power Entry
Module are set for the desired AC
Voltage Input. The assembly contains
an On/Off Switch, two 4 Amp Fuses
and three Varistors for AC line
protection. The AC is connected to
(A2) a step down Toroid that supplies
an 18 VAC output to the +15VDC/-
12VDC Power Supply Board.
4.4.4 (A3) +15V/-12V Power
Supply Board (1245-1203;
Appendix D)
The +15 VDC and -12 VDC needed to
operate the boards in the Tray are
generated on (A3) the +15 VDC/-12
VDC Power Supply Board (1245-1203).
The +15VDC/-12VDC Power Supply
Board supplies voltage regulated +15
VDC and -12 VDC Outputs to the rest
of the Tray. The Green LED DS1 is lit if
+15 VDC is present and the Green LED
DS2 is lit if -12 VDC is present at the
output of the +15V/-12V Power Supply
Board.
4.5 (A6) Metering Panel (1061456;
Appendix C)
The Metering Panel provides three
meters, one for Combined, one for Side
A Amplifier Array and one for Side B
Amplifier Array Outputs. The Side A
Meter (A15) displays the % Forward
and the % Reflected Power samples for
the Side A Amplifier Array. The Side B
Meter (A17) displays the % Forward
and the % Reflected Power samples for
the Side B Amplifier Array. The
Combined Meter (A13) displays the %
Reject, % Forward and the % Reflected
Power samples for the Combined
Output of the Transmitter. The
Metering Panel also takes the ALC
Reference Inputs from the (A4 & A5)
Variable Phase/Gain Trays and splits
them six ways which are then
connected to the UHF Amplifier Trays in
the two amplifier arrays.
The Metering Panel (A6) contains (A4,
A5, A6 & A11) four Splitter Boards
(1181-1002), (A7, A8 & A9) three Dual
Peak Detector Modules (1159965 or
1555-1271), (A10) a Visual/Aural
Metering Board (1265-1309), (A18) a
Detector Threshold Board (1245-1402)
and (A3) a ±12V Power Supply Board
(1062-1013).