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5. OPERATION
5.1 Before attemping to operate the receiver, the
information contained in this section should he
thoroughly understood by the operator. The
symbols on panel used to designate the various
controls as shown in Figure 1, should be learned
with respect to function, as described herein.
5.2 The Antenna Trimmer:-The center knob on
the left is the Antenna Trimmer. Before tuning
on any frequency range, it should be adjusted
for maximum performance on the band. This
control may be adjusted by tuning for maximum
background noise.
Occasionally it is desired to test a signal that
seems out of place, to see whether or not it is a
fundamental signal or an "image". When doing
this, if the maximum signal point coincides with
the point of maximum background noise, the
signal is a fundamental. If the control does not
affect the signal strength, or if it is a maximum
at some other point, it is an "image".
5.3 The Main Tuning Dial is on the left and con-
sists of a disc with seven scales, one for each of
the six hands and a log scale. The two low fre-
quency bands are calibrated in kilocycles and
the other four bands in megacycles.
5.4 The Vernier Tuning Dial is in the center and
has a scale with arbitrary calibrations for exact
tuning and log records of particular communica-
tion stations. It is used in conjunction with the
log scale on the main tuning dial to give addi-
tional figures for logging.
5.5 Power-Transmit-Receiver Switch: - This is a
four-position switch. Starting from fully coun-
terclockwise these positions are:
1. Power off.
2. Transmit position which gives energized
tube filaments, open plate circuits, and
shorted terminals (for transmitter relay) on
the speaker terminal board on the back of
the chassis. (3. & 4. on T.B.-2.). Connect
relay to these two terminals for transmitter
operation. (See Figure 3.)
3. Normal reception.
4. CW reception -- Beat frequency oscillator
switched on.
5.6 Selectivity Switch: - This is a five-position
switch and the band widths and control of
selectivity are illustrated in the curves of Figure
12. The five positions are:
1. I-F band width for High Fidelity, modu-
lated reception, - for "Stand-by" use.
2. I-F band width for normal modulated
reception.
3. Crystal Filter in -- for CW telegraph or
sharp modulated signal reception.
4. Crystal Filter in -- for sharper CW tele-
graph reception.
5. Crystal Filter in -- for sharpest CW tele-
graph reception.
5.7 Noise Limiter-AVC Switch: This is a four-
position switch and starting from the fully
counterclockwise position these are:
1. AVC and NL out - Manual gain only --
for CW
no interference.
2. NL on, AVC out - Manual gain
for
CW with interference.
3. NL and AVC on - for Modulated Recep-
tion with interference.
4. AVC on, NL out -- for Modulated Recep-
tion
no interference.
5.8 R-F Gain Control:-This continuously variable
sensitivity control is for use in conjunction with
the audio gain (Volume) control for all manual
gain operation. With AVC on, it should as a
rule he set to its fully clockwise position or may
be turned to eliminate interference. For recep-
tion of strong CW signals, it must he retarded
somewhat.
5.9 Noise Limiter Control:-This control sets the
instrument for operation at the required per-
centage value of Noise Limitation. The fully
clockwise position limits the noise interference
to 10070 modulation. As the knob is turned
counterclockwise, the noise interference is lim-
ited to continuously lower percentages of modu-
lation so that in the fully counterclockwise posi-
tion the Noise Limiter is operative on any
modulation whatsoever. Normally, the fully
clockwise position will be used, but under ex-
treme conditions of interference a balance point
should be found for maximum intelligibility of
signal with best modulation and least noise.
5.10 Tone Control:-This is a continuously variable
control for reducing HF response. In the fully
clockwise position the full tone is obtained and
as turned counterclockwise, high tones are
lessened. Set it to suit the particular tonal con-
ditions for the signal being received.
5.11 Beat Frequency Oscillator Control: This con-
trol is normally used for CW code signals. It
should be adjusted to give the desired audio
pitch after the signal has been accurately tuned.
5.12 Tuning: For functions of controls see the
foregoing paragraphs.
1. Turn receiver on and set the Power-
Transmit-Receive Switch for the required
type of operation.
2. Set Range Switch for band required.
3. Set Antenna Trimmer for maximum back-
ground noise.
rs)
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