Racal Instruments RA6790/GM, Техническое руководство

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Racal RA6790/GM Alignment & Tuning Manual
Page 12 of 20
h. First LO Synthesizer, Circuit Card Assembly A7.
This circuit card assembly is located in the bottom portion of the Receiver. The test
equipment required to align the assembly includes the spectrum analyzer, digital
multimeter, digital frequency counter and 50-ohm adapter, listed in Table 1-2.
(1)
Connect the digital multimeter between TP5 and ground on the A7 circuit
card assembly. Set R16 for a digital multimeter indication of 5.2 +0.01 Volts
dc.
(2) Disconnect PI of cable W2 from Jl on A2. Connect the spectrum analyzer to
PI (1st LO output) using 50-ohm adapter.
(3) Set receiver frequency to 1.046 MHz and adjust the spectrum analyzer to
observe 1 kHz sidebands on the 41.501 MHz output at a n9 dBm
level.
(4) Adjust R5 for the best rejection of "the 1 kHz sidebands. A sideband
rejection of 55 dB or more is acceptable.
(5) Disconnect the spectrum analyzer from Fl and connect the digital frequency
counter to this point. Tune the Receiver over its entire range (0.5 to 30 MHz)
and note that the digital frequency counter tracks 40.455000 MHz abve the
Receiver fr instrument error.
(6) Turn the Receiver off. Disconnect the digital frequency counter from J4 and
reconnect PI of cable W2 to Jl on A2. Disconnect the digital multimeter from
TP5.
i. Second LO/BFO Synthesizer, Circuit Card Assembly A8.
This circuit card assembly is located in the bottom portion of the Receiver. The test
equipment required to align this assembly includes the 50-ohm adapter, digital
multimeter, RF millivoltmeter and the digital frequency counter, listed in Table 1-2.
(1)
Check the links LK1 and LK2 on circuit card A8 and verify that
they are connected as required for the reference frequency IN/OUT mode of
operation. The links should be made as follows:
1 MHz - Links LK1 and LK2 linked.
5 MHz - Link LK1 open, LK2 linked.
10 MHz - Link LK1 linked, LK2 open.
(2) Make sure the REF-INT/EXT switch S2, on the rear panel, is set to the INT
position.
(3) Disconnect PI of cable W4 from J2 on A3. Connect the digital frequency
counter to Pi (2nd LO output). Connect the digital multimeter between
T P5
and ground. Set the digital multimeter to the 10 Volt dc range.
(4) Turn the Receiver on. Digital multimeter should read between 3 to 8 volts dc
(not adjustable). Digital frequency counter should read 40 MHz +20 Hz.
(5) Disconnect the digital frequency counter from PI and connect the RF
millivoltmeter with the 50-ohm adapter to PI. RF millivoltmeter should read 0
dBm +2 dB. If reading is not within the limits adjust L9 and L10 for maximum
output. Recheck RF millivoltmeter for correct indication.
(6) Disconnect the RF millivoltmeter from PI and reconnect PI of cable W4 to J2
on A3. Disconnect the digital multimeter from TP5.
(7) Set the Receiver MODE to CW and the BFO to center.
(8) Disconnect P2 of cable W6 from J5 on A4 and connect the digital frequency