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kHz +50 Hz as indicated on the digital frequency counter.
(5)
Set the AF output level to 1 milliwatt using the LINE LEVEL control on the
Receiver front panel and phone output.
(6)
Select Receiver bandwidth of 6.0 kHz (or closest bandwidth available) and
AM detector mode. Amplitude modulate the input signal 30% at 1 kHz.
(7)
Observe that the AF output level is within 5 dB of the reference set in step 5
for both line output and phone output.
(8)
Slowly rotate the AF gain control through the control range. Observe that the
phone output level varies smoothly over the full control range.
h.
Audio Distortion.
This test requires the distortion analyzer and RF signal generator listed in Table 1-2.
(1)
Disconnect digital frequency counter and connect distortion
analyzer with 600 ohm load to AF LINE output.
(2)
Set Receiver control as follows:
Power
Gain Mode
Detection Mode
BW
BFO
Receiver Tuner Frequency 1.5 MHz
(3)
Set the RF signal generator for an output of 1.5 MHz at -47 dBm, CW.
(4)
Adjust manual gain control for 1 mW output into 600 ohms. Measure
distortion. Distortion should be less than 2%.
(5)
Connect phone output from Receiver front panel to distortion analyzer and
adjust phone output for 10 mW into 600 ohms. Measure distortion.
Distortion should be less than 3%.
i.
Operation After Restoration of Power.
(1)
Carefully note the Receiver tuned frequency, BW and other displayed
functions on Receiver front panel and de-energize the Receiver.
(2)
After 1/2 hour, energize the Receiver and ensure that the Receiver returns to
the display noted in step (1).
j.
Out of Band Intermodulation Distortion.
This test requires the RF signal generator, AM/FM signal generator, step attenuator,
signal combiner and RF millivoltmeter listed in Table 1-2.
(1)
Connect the RF signal generator and AM/FM signal generator to the two
inputs of the signal combiner. Connect the output of the signal combiner to
the input of the step attenuator and its output to the RF millivoltmeter through
its RF probe.
(2)
Set the step attenuator to 5 dB then set the RF signal generator to 12.55
MHz, at a level of -10 dBm, CW. Set the AM/FM signal generator to 13.05
MHz at a level of -10 dBm, CW.
(3)
Increase the step attenuator to 70 dB. Disconnect the RF millivoltmeter from
the step attenuator and connect the RF millivoltmeter to J2 on the Receiver.
(4)
Connect the output of the step attenuator to Jl on the Receiver and tune the
Racal RA6790/GM Alignment & Tuning Manual
ON
Manual Gain
CW
3 kHz (or closest bandwidth available)
-1.00 kHz
Page 17 of 20
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