15-7
Diagnostics Theory
RF_DIAGS
Open Loop ALC Drive
This test opens the ALC loop and checks the voltage that appears on the output of the
modulator with the DAC at full scale, measured at the OUT_ALC_DRIVE using the
voltmeter referenced to the -6 Vdc measurement.
Output Detector, Detector Caps
The output capacitors are switched in and out and the output level is measured by the
voltmeter at the OUT_OUTPUT_LEVEL output.
Output Detector, Low Level
When the carrier level DAC is set to 0, there should be no RF output detected by the
voltmeter measuring at the OUT_OUTPUT_LEVEL output.
Output Frequency Range, Loop Closed
The frequency is varied and the detector voltage is measured by the voltmeter at the
OUT_OUTPUT_LEVEL output.
Bandwidth Control
Thebandwidth control bits are varied and the detected output is measured by the voltmeter
at the OUT_OUTPUT_LEVEL output.
Tracking Filter Rejection
The ALC loop is opened and the tracking filters are checked by setting the RF frequency
to the center of the two bands while changing the filter DAC to below the RF frequency
and measuring the detected level with the voltmeter at the OUT_OUTPUT_LEVEL
output.
Pulse Attenuator and Drive
This test checks the A14 Pulse Driver assembly.
Pulse Attenuator and Drive Test
A reference measurement is made and the signal is pulsed using the front panel AUDIO
OUT to drive the front panel MODULATION IN PULSE input.
13 MHz Oscillator Lock Detector
The 13 MHz VCO lock detector is measured to check the 13 MHz VCO.
Input Section
This test checks the A23 Input assembly.