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A10A1 (refer to Table 2-28 in Chapter 2).
connector J3 during these measurements, as this will unload the power supply and
could result in erroneous readings.
b.
Low Pass Filter, Assembly Al.
Test equipment required to align the low pass filter Al is the Spectrum Analyzer
listed in Table 1-2.
(1)
Connect the output of the Tracking Generator to the RF IN connector Jl of
the Receiver. Use 50-ohm cable.
(2)
Connect the output cable (A1W2) to the input of the Spectrum Analyzer,
utilizing a 50-ohm cable.
(3)
Set the Tracking Generator as follows:
Mode:
Function:
RF Output Level:
Marker Intensity:
Resolution:
(4)
Set the Spectrum Analyzer as follows:
Scan Width:
Input Attenuation:
Scan Time:
Log. Ref. Level:
Video Filter:
Scan Mode:
Scan Trigger:
(5)
Set the Marker to a frequency of 30 MHz.
(6)
Observe trace and adjust LI for maximum amplitude at the marker frequency.
(7)
Note response at 30 MHz and ensure that it is not more than 1.0 dB below
LOG REF line (see Figure 3 -1).
(8)
Set marker to a frequency of 40.455 MHz. Adjust L3 for minimum amplitude
at the marker frequency.
(9)
Set marker to a frequency of 43.19 MHz. Adjust L2 for minimum amplitude
at the marker frequency.
(10)
Set marker to a frequency of 52.30 MHz. Adjust L4 for minimum amplitude
at the marker frequency.
(11)
Compare spectrum analyzer trace with that depicted in Figure 3-1. The
shape and minimum trace points should closely approximate this shape. If
not, repeat the alignment procedures until the trace most nearly follows that
shown in the illustration.
(12)
Disconnect the test equipment and reconnect cable A1W2 to J5 on the
chassis.
Racal RA6790/GM Alignment & Tuning Manual
Marker
Track Analyzer
0 dBm
Maximum
1 kHz
0-100 Mhz
20 dB
20 Msec/Div.
0 dBm, 10 dB Log
10 kHz
Internal
Auto
Do not disconnect power output
Page 3 of 20
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