User's Manual

3300-Watt VHF Low Band Transmitter Chapter 5, Detailed Alignment Procedures
335B, Rev. 0 5-13
D. Connect a cable from the 600Ω
audio output jack of the
demodulator to the input of an
audio distortion analyzer.
2. Set the output frequency of the
audio oscillator to 400 Hz and the
output level to +10 dBm.
3. Center the aural carrier on the
spectrum analyzer with the
spectrum analyzer set to the
following:
Frequency/Division – 10 kHz
Resolution bandwidth – 3 kHz
Time/Division – 50 msec
Trigger – Free run
A. Adjust L5 for approximately
+3.5 VDC at TP2.
B. The green LED DS1 should be
illuminated, indicating a locked
condition. If not, retune L5 for
a locked condition.
4. Adjust R13, balanced audio gain, on
the aural IF synthesizer board for
±25-kHz deviation.
5. Check the distortion on the aural
distortion analyzer (THD=< 0.5%).
6. Disconnect the 600Ω balanced
audio input to the tray. Connect a
75Ω stereo audio input (400 Hz at 1
Vpk-pk) to composite audio input
jack J3 on the rear of the tray.
Follow the procedure in the stereo
generator instruction manual for
matching the level of the generator
to the exciter. Use R17 to adjust
the composite audio gain.
7. Check the distortion level on the
distortion analyzer (THD)=< 0.5%)
5.12.8 (A8) ALC Board (1265-1305;
Appendix D) (Part 1 of 2)
Table 5-1 describes the functions of each
LED on the ALC board (A8).
Table 5-1. ALC Board LEDs
LED FUNCTION
DS1 (Red LED)
Indicates that an abnormally low IF signal level is present at
IF input connector J1
DS2 (Red LED)
Indicates that the ALC circuit is unable to maintain the level
requested by the ALC reference due to excessive attenuation
in the linearity or the IF phase corrector signal path or
because jumper W3 on J6 is in manual gain
DS3 (Red LED) Indicates a video loss fault
DS4 (Red LED) Indicates that a Mute command is present
DS5 (Green LED)
Indicates that the output from the modulator is selected as
the input to the board
1. To align the ALC board, preset the
following controls on the tray:
A. ALC Board (1265-1305)
Connect jumper W1 on J4 to
disable, between pins 2 and 3 (to
disable linearity correctors).
Connect jumper W3 on J6 to
manual, between pins 2 and 3 (for
manual gain control).
Adjust R87, manual gain pot, to
mid-range.
B. IF Phase Corrector Board (1227-
1250)
Move W2 on J9 to phase
correction: enable. Move W3 on
J10 to amplitude correction:
disable.