Rtty Operation; Notch Filter - Icom IC-R71A Instruction Manual

turning the P.B. tuning control clockwise.
When receiving in the USB mode, the band width is nar-
rowed in the opposite manner. Interference from a higher
frequency will be high-pitched tones, and the P.B. tuning
control should be turned clockwise. Interference from a
lower frequency will be low-pitched tones and the P.B.
tuning control is turned counterclockwise.
This control can also be used for audio tone adjustment, so
it may be set for the most comfortable reception.
When P.B. TUNE control
is turned counterclockwise.
Receiving LSB signal
BFO frequency
Receiving signal
Interference
Interfering signal
Pass band is narrowed
and interfering signal
Receiving LSB signal
When P.B. TUNE control
is turned clockwise.
Interfering signal
BFO frequency
Interference
Receiving signal
Pass band is narrowed
and interfering signal
5-5-7 NOTCH FILTER
This circuit notches a frequency in the IF pass-band, so
this is effective to reduce interference such as a beat-tone
signal.
To use this function, push the NOTCH FILTER switch ON
and turn the NOTCH FILTER control so that the inter-
ference is reduced.
5-6 CW OPERATION
For CW reception, push the MODE SELECT SWITCH for
CW mode.
Other switches and knobs are set the same as for SSB
reception.
When the optional CW filter, FL-32, is installed, by pushing
the N (narrow) switch of the FILTER SWITCHES, the total
selectivity of CW reception is improved to 500Hz at —6aB.
goes out of the pass band.
goes out of the pass band.
Also, with this filter, internal noise is reduced for com-
fortable CW reception and an improved signal to noise
(S/N) ratio.
In addtion, a narrower crystal filter, FL-63, is optional for
this set. When you install this filter, the selectivity is
improved to 250Hz at —6dB.
The Pass Band Tuning system can be used to narrow the
band width up to 500Hz in CW mode the same as in the
SSB mode.
Also, use the Noise Blanker, AGC switch, FILTER switches
and/or PREAMP/ATT switch depending on the receiving
conditions, the same as SSB reception.
5-7 RTTY OPERATION
For RTTY operation, a teletypewriter (or an equivalent)
and a demodulator (terminal unit) which is operational
with audio input are required. Any demodulator with
2125/2295Hz filters (narrow, 170Hz shift) can be used
with the IC-R71.
Wiring for RTTY operation
Try
AF RTTY
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Audio signals for the demodulator can be supplied from
the RECORDER jack or the PHONES jack on the front
panel.
Set the operating mode for RTTY, by pushing the MODE
SELECT switch "'RTTY". The other controls are the
same as those for SSB reception. When tuning a RTTY
signal, set the TUNING RATE SELECT switch OFF (out)
position, and tune to get audio signals of 2125Hz for
MARK and 2295MHz for SPACE. (Use the tuning indica-
tor of the terminal unit for easy tuning.) Also adjust the
P.B. Tune control for clear reception.
When an optional CW narrow filter is installed, by pushing
the N switch of the FILTER switches, the narrow filter is
activated and the total selectivity of the RTTY reception
is improved (250Hz or 500Hz at —6dB depending on which
optional filter is installed) the same as the CW mode.
If you wish to receive RTTY signals which have wider shift
such as 425Hz and 850Hz shifts, prepare a demodulator
suitable for the shift and use normal FILTER switch position.
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