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Squelch Types |
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A squelch circuit is the circuit in a scanner which
prevents the receiver emitting constant background noise in the event of no
signal being transmitted. The squelch circuit mutes the audio and opens it when it
detects a valid transmission. |
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There are a maximum of six squelch modes
available on the R20 |
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Squelch Types |
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Indicated |
Setting |
Notes |
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OFF: No Indication |
Carrier Squelch only |
Set the value with SQL
button on the side |
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TSQL (<.>) |
CTCSS with audible
alert |
Bleeps when a valid
signal is received |
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TSQL |
CTCSS |
CTCSS |
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DTCS (<.>) |
DTCS with audible
alert |
Bleeps when a valid
signal is received |
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DTCS |
DTCS |
DTCS |
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VSC |
Voice Squelch Control |
Opens only when a
modulated signal is received |
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Tone squelch is
the most basic form of squelch. It's what you'd use when listening to
anything below 30MHz or to Marine VHF or civil or military airband. These
users don't use anything fancy, just good old bog standard tone squelch.
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Tone Squelch
(TSQL) is often referred to a CTCSS and is very commonly used by PBR users
in VHF and UHF.
DTCS, commonly known as DCS, is similar
to Tone Squelch but it's a more modern digital equivalent. We are starting
to see more and more users in the UK beginning to use this type of squelch
signalling. |
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VSC or Voice Squelch Control is
slightly different from all the other types in that it works by detecting the presence of a modulated
signal. This is useful for monitoring link transmissions which are always active
but only infrequently contain any audio. You can put such a frequency in a
memory channel and have it in a scan routine without the scan getting 'stuck' on
the constantly active carrier. It is, however, relatively slow in operation and
will slow down the scan routine. |
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Changing Squelch Type |
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Press and
hold the [
TONE ] button for one second until you hear a
bleep. The squelch type should cycle through the types shown in the table
above.
If no type is shown, then you are in carrier
squelch mode
All squelch types can be un-muted by pressing the
[SQL]
button on the side of the radio. |
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Not all types are available in all modes. In
fact, in it only narrow FM which has all six types of squelch available to the
user. All other modes
offer only tone and VSC squelch options. This makes sense really as you would not
encounter CTCSS or DTCS on WFM, SSB or CW. |
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There is a whole section
in this R20 guide covering |
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Subtone Signalling |
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You can learn more about
subaudiable tone and code squelch in |
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A beginner's guide to scanning |
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