Icom IC-R75 Instruction Manual - Page 20

Preamp, Attenuator, AGC time constant, Antenna selection

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5 RECEIVE FUNCTIONS ■ Preamp The preamp amplifies received signals in the front end circuit to improve the S/N ratio and sensitivity. Turn this function ON when receiving weak signals. ➥ Push [P.AMP] to toggle between preamp-1 and preamp-2 or turn the preamp OFF. ■ Attenuator The attenuator prevents desired signals from distorting when very strong signals are near the desired frequency or when very strong electric fields, such as from broadcasting stations, are near your location. ➥ Push [ATT] toggle the 20 dB attenuator function ON and OFF. • "ATT" appears when the attenuator is turned ON. ■ AGC time constant The AGC (Automatic Gain Control) controls receiver gain to produce a constant audio output level even when the received signal strength is varied by fading, etc. Use AGC slow for normal phone operation; AGC fast for receiving data and searching for signals. ➥ Push [AGC] momentary to toggle the AGC time constant between fast and slow. • "F.AGC" appears when the fast time constant is selected. • "AGC" appears when the slow time constant is selected. ➥ Push [AGC] for 2 sec. to turn the AGC circuit OFF. • "AGC OFF" appears when the AGC circuit is turned OFF. • Push [AGC] to turn the AGC circuit ON. • S-meter is deactivated when the AGC circuit is turned OFF. ■ Antenna selection 2 types of antenna can be connected to this receiver. When 2 antennas are connected, select an antenna depending on the operating condition. ➥ Push [ANT(SET)] for 2 sec. to toggle between the antenna 1 and 2 connectors. • If a blank memory channel has been selected, push [V/M] to select VFO mode in advance. 16 USB R X PREAMP 1 ANT 1 AGC BLANK S1 3 5 7 9 20 40 60dB VFO "PREAMP" appears while the preamp is activated. USB R X ATT ANT 1 AGC BLANK S1 3 5 7 9 20 40 60dB VFO "ATT" appears while the attenuator is activated. USB R X ANT 1 F. AGC BLANK S1 3 5 7 9 20 40 60dB VFO "F.AGC" appears when the fast time constant is selected. USB R X ANT 1 AGC BLANK S1 3 5 7 9 20 40 60dB VFO "ANT1" appears when the [ANT1] connector is in use.

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16
5
RECEIVE FUNCTIONS
■
Preamp
The preamp amplifies received signals in the front
end circuit to improve the S/N ratio and sensitivity.
Turn this function ON when receiving weak signals.
➥
Push [P.AMP] to toggle between preamp-1 and
preamp-2 or turn the preamp OFF.
■
Attenuator
The attenuator prevents desired signals from
distorting when very strong signals are near the
desired frequency or when very strong electric fields,
such as from broadcasting stations, are near your
location.
➥
Push [ATT] toggle the 20 dB attenuator function
ON and OFF.
• “ATT” appears when the attenuator is turned ON.
■
AGC time constant
The AGC (Automatic Gain Control) controls receiver
gain to produce a constant audio output level even
when the received signal strength is varied by fading,
etc. Use AGC slow for normal phone operation; AGC
fast for receiving data and searching for signals.
➥
Push [AGC] momentary to toggle the AGC time
constant between fast and slow.
• “F.AGC” appears when the fast time constant is
selected.
• “AGC” appears when the slow time constant is
selected.
➥
Push [AGC] for 2 sec. to turn the AGC circuit OFF.
• “AGC OFF” appears when the AGC circuit is turned
OFF.
• Push [AGC] to turn the AGC circuit ON.
• S-meter is deactivated when the AGC circuit is turned
OFF.
USB
R X
BLANK
BLANK
S1
3
5
7
9
20
40
60
dB
AGC
ANT
VFO
1
PREAMP 1
“PREAMP” appears while the
preamp is activated.
■
Antenna selection
2 types of antenna can be connected to this receiver.
When 2 antennas are connected, select an antenna
depending on the operating condition.
➥
Push [ANT
(SET)
] for 2 sec. to toggle between the
antenna 1 and 2 connectors.
• If a blank memory channel has been selected, push
[V/M] to select VFO mode in advance.
USB
R X
BLANK
BLANK
S1
3
5
7
9
20
40
60
dB
AGC
ANT
VFO
1
“ANT1” appears when the
[ANT1] connector is in use.
USB
R X
BLANK
BLANK
S1
3
5
7
9
20
40
60
dB
AGC
ANT
VFO
1
ATT
“ATT” appears while the attenuator
is activated.
USB
R X
BLANK
BLANK
S1
3
5
7
9
20
40
60
dB
AGC
ANT
VFO
1
F. AGC
“F.AGC” appears when the fast time
constant is selected.