User's Manual

Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures
DT835A, Rev. 1 5-8
5.3.1 (A2-A1) Variable Gain/Phase
Board (1265-1425; Appendix D)
The board is mounted in (A2) the
variable gain/phase enclosure. The board
has an AGC adjustable gain of 0 to 20
dB.
5.3.2 (A3-A1) 1-Watt UHF Amplifier
Board (1227-1303; Appendix D)
The board is mounted in (A3) the 1-watt
UHF amplifier enclosure. There are no
adjustments to this board; it has
approximately 10 dB of gain.
5.3.3 (A1) UHF Filter (1007-1101;
Appendix D)
Apply a multiburst test signal to the
transmitter. Monitor J2 with a spectrum
analyzer and tune C1 and C3 for peak
output with a flat-frequency response.
5.3.4 (A4-A1) Single Stage Amplifier
Assembly, Class A (1265-1418, low
band/1265-1416, mid band/1265-
1417, high band; Appendix B)
This assembly is made from a generic
single stage amplifier board, class A
(1265-1415) with a frequency
determining kit.
The generic single stage amplifier board
operates class A and has a gain of
approximately 11 dB. The bias of the
transistor is set by the on-board biasing
circuit. Adjust R6 for 5 amps of idle
current, no RF drive applied. Connect a
voltage meter across E1 and E2 on the
amplifier protection board and move
switch S1 to the I1 position; adjust R6
for a reading of 50 mV. Connect a sweep
test signal to J1, the RF input jack of the
UHF amplifier tray and monitor the
output of the board at J2 with a padded-
input spectrum analyzer. Tune capacitor
C5 for peak output and then tune C6 for
peak output power with a flat-frequency
response at J2.
5.3.5 (A4-A2) Coupler Board
Assembly (1227-1316; Appendix D)
There are no adjustments to this board.
5.3.6 (A4-A3) Dual Stage Amplifier
Assembly, Class AB (1265-1413, low
band/1265-1411, mid band/1265-
1420, high band; Appendix D)
This assembly is made from a generic
dual stage amplifier board, class AB
(1265-1404) with a frequency
determining kit.
The generic dual stage amplifier board
operates class AB and has a gain of
approximately 9 dB. The biases of the
transistors are set by the on-board
biasing circuits. Adjust R106 and R206
100 mA digital of idle current per side, no
RF drive applied. Connect a voltage
meter across E1 and E2 on the amplifier
protection board and move switch S1 to
the I3 position; adjust R106 for a reading
of 1 mV digital. Move switch S1 to the I2
position and adjust R206 for a reading of
1 mV digital. Depending on the linearity
of tray, these transistors may have 50
mA digital of bias. Connect a sweep test
signal to J1, the RF input jack of the UHF
amplifier tray, and monitor the output of
the board at J2 with a padded input to a
spectrum analyzer. Tune capacitors C105
and C205 for peak output and then tune
C119 and C219 for peak output with a
flat-frequency response and minimum
current at J2.
5.3.7 (A5-A1) 4-Way Splitter
Assembly (1265-1432; Appendix D)
There are no adjustments to this
assembly.
5.3.8 (A5-A2, A5-A3, A5-A4, and A5-
A5) Dual Stage Amplifier Assemblies,
Class AB (1265-1439, low
band/1265-1440, mid band/1265-
1441, high band; Appendix D)
Each board is made from a generic dual
stage amplifier board, class AB (1265-