Racal Instruments RA-117 User Manual page 34

SIGNAL-TO-NOISE TEST
7. Perform a signal-to-noise test as follows:-
(1) Set the receiver controls as follows:-
(2) Set the controls of the output meter for an impedance oa 3 ohms and a power
range of 60mW and connection it to the 1W 3 ohm output terminals of the
receiver.
(3) Set the controls of the signal generator for a c.w output of 1 V at 1 5 Mc/s and an
impedance of 75 ohms. Connect the output of the signal generator to the receiver
antenna input socket.
(4) Tune the receiver to the output frequency of the signal generator and adjust the
R.F./I.F. GAIN control a reading of 50mW on the output meter.
(5) Switch off the input signal and check that the output meter does not reade more
than 0.82mW.
(6) Repeat the test with a 30% modulated signal at a level of 3.5 V and the receiver
B.F.O. switched off.
(7) Perform signal-to-noise ratio tests at 3 5, 6 5, 12 5 and 24 5 Mc/s.
A.V.C. TEST
8. Perform a test of the A.V.C. circuits as follows:-
(1) Set the controls of the receiver as follows:-
(2) Set the controls of the output meter for an impedance of 3 ohms and power range
of 200mW. Connect the meter to the 1W 3-ohm terminals of the receiver.
General Servicing and Aligment Procedures
R.F. RANGE
MEGACYCLES
KILOCYCLES
R.F. ATTENUATOR
SYSTEM switch
BANDWIDTH
B.F.O. switch
B.F.O. NOTE
A.F. GAIN
SPEAKER
R.F. RANGE
MEGACYCLES
KILOCYCLES
R.F./I.F. GAIN
R.F. ATTENUATOR
SYSTEM switch
A.V.C. switch
BANDWIDTH
B.F.O. switch
1 – 2 Mc/s
1
500
MIN.
MAN.
3 kc/s
ON
1 kc/s
fully-clockwise
OFF
2-4 Mc/s
3
500
fully-clockwise
MIN.
A.V.C.
SHORT
3 kc/s
OFF
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