Racal Instruments RA6790/GM, Техническое руководство

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Racal RA6790/GM Alignment & Tuning Manual
Page 11 of 20
(3) Adjust R19 and R23 to the full clockwise positions. Cancel MAN AGC and
note the indication of the RF millivoltmeter. RF millivoltmeter should read 70
+10 millivolts.
(4) Reduce the AM/FM signal generator output to -113 dBm (0.5 uVolts). Select
MAN AGC, cancel SHORT AGC, adjust R19 for 64 +10 millivolts indication
on RF millivoltmeter.
(5) Connect the digital multimeter to TP9 on A5. Cancel MAN AGC, select
SHORT AGC. Increase AM/FM signal generator output to -78 dBm (30
uVolts). Set R23 for an indication of 8.5 +0.05 Volts dc on the digital
multimeter.
(6) Disconnect the AM/FM signal generator from Jl-RF IN, the digital multimeter
from TP9 and the RF millivoltmeter from TP7.
(7) Disconnect PI of cable Wll from J3 and A4. Connect the tracking generator
to Jl and connect the spectrum analyzer to TP7 on A5, using the high Z
probe. Adjust the spectrum analyzer as follows:
Output Level:
-54 dBm (tracking generator)
Center Frequency: 455 kHz
Input Attenuation: 10 dB
Sweep Width: 20 kHz/div.
Bandwidth: 3 kHz/div.
Log Ref. Level: 0 dBm
Log/Lin Switch: 10 dB Log
(8) Set AGC to MAN and the IF GAIN control for approximately -6 dBm on the
spectrum analyzer. While observing the spectrum analyzer trace, adjust LI
and L2 to obtain the bandpass waveform shown for Step 12 of the L4
adjustment procedures in Paragraph e. If a double peak is obtained the
trough should be no greater than 0.5 dB below the peaks.
(9) Disconnect the tracking generator from Jl and reconnect P2 of cable Wll to
J3 on A4. Disconnect PI of cable Wl from J7 on chassis (output of A3) and
connect the tracking generator to PI.
(10) With the tracking generator/spectrum analyzer controls adjusted as
described in Step 7 and the LSB mode selected on the Receiver, adjust the
IF GAIN control for approximately -6 dBm. Refer to Table 3-1 for the LSB
filter passband and stopband characteristics and ensure that the spectrum
analyzer trace display meets those characteristics.
(11) Turn the Receiver off. Disconnect the tracking generator from PI and
reconnect PI of cable Wl to J7 on chassis. Disconnect the spectrum analyzer
from TP7.
g. Remote Interface and Microprocessor, Circuit Card Assemblies A6A1
and A6A2.
The remote interface card (A6A1) is an optional assembly and may
or may not be installed in the Receiver. When it is used, both the A6A1 and
A6A2 cards are mounted on the right hand side of the top portion of the
Receiver. These two circuit cards do not contain any variable components
and therefore do not require any alignment or adjustment.