Icom IC-R71A Instruction Manual page 17

When you wish to operate on another MHz band than the
displayed one, push the BAND SELECT FUNCTION
switch in, then turn the TUNING CONTROL so that the
desired MHz band is displayed.
Slowly turn the AF GAIN control clockwise to a comfor-
table level. Rotate the tuning knob until a signal is received.
The meter needle will move according to the signal strength,
so tune for the highest possible meter reading and the
clearest audio. If you cannot get a clear signal, you may be
receiving in the opposite sideband. If so, change the mode
to the proper sideband.
Adjust the RF GAIN control and TONE control for com-
fortable reception. 2
If squelch operation is required to cut out noise when no
signal is received, turn the SQUELCH control ctockwise
until the noise from the speaker stops and leave it just
below this threshold.
For tuning, memory channel operation and scanning opera-
tion, please refer to 5 - 1 HOW TO TUNE on page 9.
5 - 2 MEMORY CHANNEL OPERATION on page 11,
5 - 3 FREQUENCY SETTING BY KEY PAD on page 13
and 5-4 SCANNING OPERATION on page 13.
5-5-2 NB (NOISE BLANKER)
When there is pulse type noise, such as ignition noise from
automobile motors, turn the NB LEVEL control clockwise
and click ON, so that noise will be suppressed and even
weak signals will be received comfortably.
When the NB switch is set in the WIDE (locked in) position,
the noise blanker will effectively work for ''woodpecker's
noise', however, if the receiving signal is too strong, the
noise blanker may work with the receiving signal itself, and
some distortion may occur in the receiving audio or keying
form. At this time, set the N.B. Switch in the out position,
or turn the NB LEVEL control completely counterclock-
wise (Off position).
5-5-3 AGC (AUTOMATIC GAIN CONTROL)
The IC-R71 has a fast attack/slow release AGC system
which holds the peak voltage of rectified IF signals from
the IF amp circuit for a certain period. Therefore, during
the pauses in normal speech of the receiving signal, uncom-
fortable noise will not be heard. The meter indicates the
peak value for a certain period, facilitating reading of the
meter ''S"' function.
For normal SSB reception, turn the AGC TIMING Switch
to the SLOW position. Turn the AGC TIMING Switch
to the FAST position, when tuning or receiving signals with
short interval fading. When in the FAST position, the
time constant is shortened.
When this switch is set at the OFF position, the AGC
circuit is turned OFF, and the S-meter does not work even
if a signal is received. However the RF GAIN control is still
active and the needle of the meter moves depending on the
control position.
5-5-4 PREAMP/ATT SWITCH
Slide the PREAMP/ATT Switch to the PRE position when
receiving weak signals. In the PRE position, an RF pream-
plifier is inserted into the receiving antenna circuit, increas-
ing sensitivity and giving easy reception.
Slide the PREAMP/ATT switch to the ATT position when
strong nearby signals disturb signal reception or make "'S"
reading difficult. In the ATT position, the RF amplifier is
removed from the circuit and a 20dB attenuator is inserted
into the receiving antenna circuit, reducing interfering
signals and giving more stable reception. In normal opera-
tion the PREAMP/ATT switch is left in the OFF position.
5-5-5 FILTER SWITCHES
These switches select three conditions as follows;
NORMAL _ Both switches are OUT position or pushed in.
WIDE The W (wide) switch is pushed in.
NARROW — The N (narrow) switch is pushed in.
A filter is selected in each condition. The selectivity and
Pass-Band-Tuning function will be as follows;
BAND WIDTH
2.3KHz
2.8KHz
FILTER SWITCH PBT CONTROL
NORMAL EFFECTIVE
WIDE INOPERATIVE
NARROW EFFECTIVE
* When optional CW filter, FL-32 is installed.
5-5-6 P.B. (PASS-BAND) TUNING
Pass-Band Tuning is a system to narrow the band width
(selectivity) of the frequencies that will pass through the
crystal filter electronically from either the upper or lower
side continuously by up to 500Hz. This is very effective in
reducing interference from nearby signals.
To use the PBT system, rotate the PBT control clockwise
or counterclockwise depending on the interfering signals.
The center (12 o'clock) position is the widest position.
For example, while receiving in the LSB mode, if you get
interference from a lower frequency (interfering signals are
high-pitched tones), narrow the band width by turning the
P.B. tuning control counterclockwise. When the interfer-
ing signals are low-pitched tones, they are from a higher
frequency, and you should narrow the band width by
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