
knob from the off position moves the rejection notch across the
re-
ceiver
pass
band .
11.
The
accessory
switch turns on the S-NB Noise Blanker and the SCC-4
Crystal Calibrator if they are installed. The 5-NB and the SCC-4 are
off in the NORM position.
3.2
SIMPLIFIED OPERATING PROCEDURE
As an example , suppose that the SPR-4 is to be tuned to 7272 kHz. First
turn the crystal selector
dial
to the 7.0 MHz position. Set the
preselec-
tor to 5.5 as indicated on the second line of the crystal selector dial .
Next set the range switch to E as indicated on the bottom line of the
crystal selector dial.
Turn the tuning knob until the 100 kHz
dial
is
be-
tween 2 00 and 300 and the
one
kHz
dial
is on 72. Select the desired
mode of reception with the mode switch.
The RF gain control should be
full clockwise and the notch should be in the off position. Turn on the
receiver with the audio gain control and adjust it for normal audio output.
Fine
tune
the preselector for maximum indication of the S-meter.
The frequency of the received signal is the sum of thè crystal
dial
read-
ing and the main tuning
dial
reading as shown by the example:
Crys
ta1
Selector Reading
7 .000 MHz
100 kHz
Dial
Reading .200
1 kHz
Dial
Reading
.072
Frequency of Received Signal
7.272 MHz
3.3
DIRL
CALIBRATION
The main tuning
dial
calibration
may
be adjusted over a short frequency
range by using the known frequency of the SCC-4 crystal calibrator or a
station such as the National Bureau of Standards
,
WWV,
on 2.5, 5, 10,
15, 20, and 25 MHz.
Usually 5 and 10 MHz WWV signals are the
easi-
est to receive .
With the mode switch in the CW, LSB or USB position,
tune
the signal from the SCC-4 or
WWV
to zero beat. Hold the main
tuning knob stationary and
rotate
the
skirt
until the
dial
reads the correct
frequency .
-
12-
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