Icom IC-730 Instruction Manual page 16

5 - 2 - 2 NB (NOISE BLANKER)
Turn the noise blanker ON (in) when there is pulse type
noise, such as ignition noise from automobile motors. Noise
will be suppressed and even weak signals will be received
comfortably. When the N.B. WIDTH switch, located under
the access cover, is set in the WIDE 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 cause in the receiving audio or keying form.
At this time, set the N.B. WIDTH Switch in the NARROW
position, or turn the NB switch OFF.
5 - 2 - 3 AGC (AUTOMATIC GAIN CONTROL)
The IC-730 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 received signal, uncomforta-
ble 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, set the AGC switch in the OUT
(slow) position. Set the AGC Switch in the FAST (IN)
position, when tuning or receiving signals with short interval
fading. When in the FAST position, the time constant is
shortened.
5 - 2 - 4 PREAMP SWITCH
Turn the PREAMP Switch ON (in) when receiving weak
signals. In the ON position, an RF preamplifier is inserted
into the receiving antenna circuit, increasing sensitivity and
giving easy reception.
5 - 2 - 5 PASS-BAND SHIFT CONTROL
Pass-Band Shift Control is a system in the receive mode to
shift the pass-band of the IF upper or lower side continu-
ously. This is very effective in reducing interference from
nearby signals.
To use the Pass-Band Shift system, slide the control toward
right or left side. The center position is the normal pass-
band condition.
For example, while receiving in the LSB mode, if you get
interference from a lower frequency (interfering signals are
high pitched tones), shift the pass-band by sliding the P.B.
SHIFT control left side. When the interfering signals are low-
pitched tones, they are from a higher frequency, and you
should shift the pass-band by sliding the P.B. SHIFT control
right side.
When receiving in the USB mode, the pass-band is shifted
in the opposite manner. Interference from a higher fre-
quency will be high-pitched tones, and the P.B. SHIFT
control should be slid right side. Interference from a lower
frequency will be low-pitched tones and the P.B. SHIFT
control is slid left side.
This control can also be used for audio tone adjustment, so
it may be set for the most comfortable reception.
When the optional crystal filter, FL-30, is installed, the Pass-
Band Shift system will be changed the Pass-Band Tuning
system.
The Pass-Band Tuning (PBT) is a system in the receive
mode to narrow the band width (selectivity) of the
frequencies that will pass through the crystal filter electrically
from either the upper or lower side continuously by up to
800Hz. This is very effective in reducing interference from
nearby signals.
To use the PBT system, slide the control the same as the
Pass-Band Shift system.
The center position is the widest position and is equivalent to
the normal SSB band width.
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