Specifications

B. Deviation Adjustment Using a Spectrum Analyzer.
1. If the spectrum analyzer has a high impedance input, connect it to the baseband signal at
any convenient point after the insertion of the subcarrier to be adjusted. If the
measuring instrument has a low impedance (i.e., 75 or 50 ohm) it is necessary to
connect the instrument to an isolated monitor point in order to prevent the additional
load presented by the low impedance input from affecting the levels of the signals
on the baseband (this level change has no direct effect on the adjustment of
subcarrier deviation, and may be ignored if there are no active receive sites that may
be adversely affected).
2. Connect an audio signal generator to the T, R, and ground connections of the channel to
be adjusted. The audio signal generator should be set to provide a 13.587 kHz test
signal at the following amplitude:
Setup Amplitude for test signal
Compressor IN Peak Program Level (PPL)
Compressor OUT 15.36 dB below PPL
(75µS Emphasis)
Compressor OUT 11.31 dB below PPL
(CCITT J.17 Emphasis)
3. Temporarily disconnect the audio signal generator. Tune the spectrum analyzer to the
frequency of the subcarrier to be adjusted. The spectrum analyzer should be set for
a scan width of not greater than 20 kHz per horizontal division, and not less than 5
kHz per horizontal division, and the bandwidth should be no greater than 3 kHz.
Verify that the desired carrier is clearly visible at the exact center of the analyzer
screen. Adjust the gain/attenuation settings of the analyzer so that the peak of the
carrier is near the top of the screen, and the vertical resolution is 10 dB per division.
Reconnect the audio signal generator. Sidebands of the carrier frequency should be
visible at 13.587 kHz intervals on the screen. The center (carrier) signal may or
may not be visible, depending on the existing adjustment of the front panel DEV
control. Adjust the front panel screwdriver adjustment DEV for a minimum level
(null) at the center (carrier) frequency. You have now adjusted the deviation for
exactly 75kHz peak (150kHz peak-to-peak).
4. If the second channel of the 450 Transmitter is also to be adjusted, repeat steps 2. and
3., above.
450 Operation Manual Rev A Page 25 8/26/99