Racal Instruments RA6790/GM, Техническое руководство

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Racal RA6790/GM Alignment & Tuning Manual
Page 8 of 20
generator to .5 uV. Note reading of RF millivoltmeter.
Increase output of AM/FM signal gen120 dB in 10 dB steps and
assure
that reading on RF millivoltmeter remains within 3 dB of that obtained at the
.5 uV RF input level.
(12) Remove the link between the filter input and output sockets and reinstalls the
filter previously removed. Determine the bandpass filters installed in the
Receiver.
(13) In order to examine the bandpass characteristics of the filters, the tracking
generator and spectrum analyzer must be used in the same manner as in
Step 4 above. Set the tracking generator/spectrum analyzer as follows:
Frequency:
455 kHz
TG Level: 40 dBm
Input Attenuation: 30
Log. Ref. Level: 0, 10 dB/Log .
Linear Sensitivity: Adjusted to set trace at 0 Log marker on display.
Scan Time: .5 Seconds
Scan Width/Div. See Chart Below
Bandwidth: See Chart Below
Video Filter: 10 Hz
(14) Ensure that the Receiver is in manual gain and that the IF Gain control is at
maximum CW rotation. Select each filter position via the MODE panel.
Observe the trace on the spectrum analyzer for each filter selected. It may
be necessary to adjust the IF gain control to avoid distortion of the IF
passband. Table 3-1 provides the passband maximum and minimum va lues
for the 3 dB and 60 dB points. Note that the Scan width and Bandwidth will
have to be adjusted to each filter as follows:
Filter B/W Scan Width/Div. Bandwidth
400 H z 0.5 kHz 0.3 kHz
1000 Hz 0.5 kHz 0.3 kHz
1200 Hz 0.5 kHz 0.3 kHz
2.0 kHz 1.0 kHz 1.0 kHz
3.0 kHz 1.0 kHz 1.0 kHz
3.2 kHz 1.0 kHz 1.0 kHz
6.8 kHz 2.0 kHz 1.0 kHz
16 kHz 5.0 kHz 3.0 kHz
USB/LSB 1.0 kHz 1.0 kHz
(15) If the A5 ISB option is installed, the LSB filter must be checked by using the
HI-Z probe on TP7 of the A5 board. Ensure that the Receiver is in the LSB
mode.
(16) Disconnect all test equipment. Restore cable W1P1J6 to coaxial fitting J6
on the chassis.
(17) Connect AM/FM signal generator to the Receiver RF input jack Jl. Attach the
junction box to connector J3, AF OUT, on the rear of the Receiver. Connect
the input of the distortion analyzer to the BNC connector labeled "MONITOR"
on the junction box. Set the distortion analyzer Function Switch to Voltmeter