7-16 Adjustments 8525B/8528 Technical Service Manual
Issue 6 Publication No: 15-02036
7.4 Receiver Performance Checks
7.4.1 Sensitivity and Signal + Noise to Noise Ratio
Connect an AC voltmeter across the audio output. Set the signal generator to
0.35µV PD output, connect it to the antenna socket and adjust the frequency
to produce a 1kHz audio output.
Adjust the signal generator to a frequency outside the receiver passband and
check that the audio output drops by at least 10dB.
7.4.2 AGC Check
Reset the signal generator output to 50mV PD and adjust the frequency to
produce a 1kHz audio output. Reduce the volume to a convenient level.
Reduce the signal generator output until the receiver output drops by 6dB.
The signal generator level should be less than 2.5µV PD.
7.4.3 Audio Output
Increase the signal generator output to 50µV PD, adjust the frequency for
1kHz audio output. The audio output should exceed 4V RMS at the onset of
clipping, as displayed on a CRO.
7.4.4 Selectivity (USB Operation)
Set the signal generator output to 0.5µV PD and note the audio output
reference level. Increase the signal generator output 60dB and, using the
Frequency Counter on the signal generator, adjust the frequency to −1kHz
and then to +4.2kHz from SCF. At these points the audio output should be
less than reference level.
7.4.5 Clarifier Operation
With an input signal of SCF +1kHz (SCF preferably greater than 10MHz)
adjust clarifier and ensure frequency shifts of 0.001% (l0ppm) can be made
in the type 8525B/8528, or 180Hz in the 8528S.
7.4.6 Noise Limiter Operation
Connect a BNC T-piece into the 50Ω coax from the signal generator to the
transceiver. To the unoccupied socket add a BNC to two-terminal adaptor.
Connect the output from a square-wave generator at a level of 5Vpp at
100Hz via a 100pF capacitor to the adaptor.
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