Good explanation...I'll just add that some scanners do offer a CTCSS feature
so that you only hear the transmissions of interest, but most do not.
Certainly you do not NEED a CTCSS-equipped scanner to monitor transmissions
using CTCSS tones.

- Doug


"Rick" wrote in message
...
On 21 Jul 2004 00:17:52 -0700, (Jim) wrote:

Hi all,

Hope someone can clear up my confusion when using CTCSS.
1. Is it possible to use same frequency by multiple parties
simultaneously?
2. Can scanner detect CTCSS initiated signals?

TIA.
Jim


Jim;

CTCSS (Continuous Tone Controlled Squelch System) is just a method of
controlling the squelch on a receiver.

If you have ever used a CB radio, you know that the squelch control
simply adjusted the level which was required by an incoming signal
before it would break through the squelch and be heard.

If the CB channels were very busy you would have to turn up the
squelch higher to stop the background noise, and then only strong
signals would break the squelch. However when the signal did break the
squelch you could here all the whistling and squealing of the other
conversations on the channel although they were usually weaker than
the strong signal which just broke the squelch.

In a CTCSS receiver, the squelch does not work based on the strength
of the signals. Instead the transmitter send a continuous sub-audio
tone of a particular frequency during each transmission. The squelch
on the receiver will never be broken unless it detects that particular
tone in a transmission. At that time you will still hear all the other
communications on that channel. In the case of CTCSS however, the
transmission you want to listen to could actually be weaker than some
other transmissions, and thereby very hard to understand.

A scanner will pick up every signal from an FRS radio because it's
squelch is based on signal strength. It is not waiting for any
particular tone, and doesn't even know they exist in the transmission.

Setting the sub channel on an FRS radio to 0 , tells the receiver not
to look for any tones, just open up the squelch when you hear anything
on the channel. I often use this setting when traveling to try and
pick up any conversations in the area. If I find a conversation I can
just sit and listen or if I wish to talk to the parties, I have to run
through the 38 sub-channels to find the one the people are actually
using. Otherwise I would not break their squelch when I transmitted.

I hope this helps.

Rick
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