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Receiver to 12.55 MHz.
(5)
Adjust the manual IF gain control on the Receiver for a -10 dBm reading on
the RF millivoltmeter.
(6)
Tune the Receiver to 12.05 MHz and set step attenuator to 5 dB. Note that
the RF millivoltmeter reads 65 dB below reading in step 5.
(7)
Tune the Receiver to 13.05 MHz and note that RF millivoltmeter reads 65 dB
below reading in step 5.
k.
Audio Output Power.
This test requires the AM/FM signal generator, the junction box and the power
meter listed in Table 1-2.
(1)
Connect the AM/FM signal generator to Jl on the rear panel and set to
29.550 MHz at -97 dBm level and AM modulated at 30%.
(2)
Turn Receiver on and tune to 29.550 MHz. Set AGC to medium and select
6.8 kHz bandwidth. Rotate AF control on front panel to maximum clockwise
position.
(3)
Connect the junction box to connector J3 on the Receiver rear panel and
connect the power meter to MONITOR connector on the junction box.
(4)
Note that power meter reads at least 1 milliwatt.
(5)
Disconnect power meter from MONITOR connector and connect it to L/S
OUT (loudspeaker).
(6)
Note that power meter reads at least 1 watt.
(7)
Disconnect power meter from L/S OUT and connect it to the PHONES jack
on the front panel.
(8)
Note that power meter indicates at least 10 milliwatts.
(9)
Rotate AF control through its complete range and note that phone output
level varies smoothly.
l.
Noise Figure.
This test requires the noise generator, 50 ohm adapter and RF millivoltmeter listed
in Table 1 -2.
(1)
Connect the RF millivoltmeter with the 50 ohm adapter to connector J2 on
Receiver rear panel.
(2)
Connect the noise generator to connector Jl on the Receiver rear panel.
Turn the noise generator on and adjust for 15.5 MHz at a low level•
(3)
Turn Receiver on, tune to 15.5 MHz, select 6.8 kHz bandwidth, CW, BFO +1
kHz and maximum IF gain.
(4)
Note reading on RF millivoltmeter, then increase noise generator output
level until RF millivoltmeter reading increases by 3 dB.
(5)
Noise figure shall be no greater than 12 dB.
m.
RF Input Impedance.
This test requires the RF signal generator and vector impedance meter listed in
Table 1 -2.
(1)
Connect the RF signal generator output to the RF input of the vector
impedance meter.
(2)
Connect the vector impedance meter probe to Jl connector on Receiver rear
Racal RA6790/GM Alignment & Tuning Manual
Page 18 of 20
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