General Servicing and Aligment Procedures
34
SIGNAL-TO-NOISE TEST
7. Perform a signal-to-noise test as follows:-
(1) Set the receiver controls as follows:-
R.F. RANGE
1 – 2 Mc/s
MEGACYCLES
1
KILOCYCLES
500
R.F. ATTENUATOR
MIN.
SYSTEM switch
MAN.
BANDWIDTH
3 kc/s
B.F.O. switch
ON
B.F.O. NOTE
1 kc/s
A.F. GAIN
fully-clockwise
SPEAKER
OFF
(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
µ
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
µ
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:-
R.F. RANGE
2-4 Mc/s
MEGACYCLES
3
KILOCYCLES
500
R.F./I.F. GAIN
fully-clockwise
R.F. ATTENUATOR
MIN.
SYSTEM switch
A.V.C.
A.V.C. switch
SHORT
BANDWIDTH
3 kc/s
B.F.O. switch
OFF
(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.
Summary of Contents for RA-117
Page 1: ...Racal RA 117 Radio Receiver...
Page 24: ...Detailed Circuit Description 24 at maximum is the correct calibration maintained...
Page 32: ...32...
Page 70: ...Illustrations 70...
Page 71: ...Illustrations 71...
Page 72: ...Illustrations 72...
Page 73: ...Illustrations 73...
Page 74: ...Illustrations 74...
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