Icom IC-F521 Instruction Manual page 8

Vhf/uhf transceiver
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1
PANEL DESCRIPTION
[ T A ]
TALK AROUND KEY
Turns the talk around functon ON and OFF.
• The talk around functon equalses the transmt
frequency to the receve frequency for moble-
to-moble communcaton.
[CALL]
CALL KEYS
Transmt a 2-tone code.
• Call transmsson s necessary before you call
another staton dependng on your sgnalng
system.
[EMER]
EMERGENCY KEY
Push and hold the key to transmt an emergency
call.
• If you want to cancel the emergency call, push
(or push and hold) the key agan before trans-
mttng the call.
• The emergency call s transmtted one tme
only or repeatedly untl recevng a control code
dependng on the pre-settng.
5
[CODE]
TX CODE CHANNEL UP/DOWN KEY
Push to selects a TX code channel drectory.
[DTMF]
DTMF CHANNEL SELECT KEY
Push ths key to select a DTMF channel.
• Push ths key, then select the desred DTMF
channel usng the [
Push the key to transmt the selected DTMF
code.
[TONE]
C. TONE CHANNEL ENTER KEY
Push ths key then nput a contnuous tone
memory channel number usng [
to change the tone frequency.
]/[
] keys.
]/[
] keys

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Questions and answers

Paul Stein
January 29, 2025

How to control squech

1 comments:
Mr. Anderson
February 10, 2025

The squelch on the Icom IC-F521 is controlled by a noise squelch circuit. This circuit detects noise components in the AF signals and switches the AF mute switch accordingly. The squelch level is managed by a level controller (IC6, pins 21, 22), which processes signals from the FM IF IC (IC1, pin 9) and applies them to an active filter section (IC1, pin 8). Noise components around 10 kHz are amplified and converted into pulse-type signals by the noise detector section.

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