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

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
To reply by email, please remove the first "R" in my return address

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
To reply by email, please remove the first "R" in my return address

On Wed, 21 Jul 2004 11:57:30 GMT, "DougSlug"
wrote:

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.

It can, however, be helpful to have at times.

Where I live, I'm halfway between two localities whose police
departments use the same frequency but different CTCSS tones. They are
in neighboring counties and don't interfere with one another's
operations, but inasmuch as I am on the border between the two
counties, I can hear both dispatchers.

Trobule is, I'm really only interested in monitoring one of the two,
because as a ham involved in ARES/RACES, I'm listening to the one in
my county of residence.

Since I have a CTCSS-enabled scanner (PRO-2045 with the optional CTCSS
board installed), I only have to listen to the one I want to hear, and
my scanner isn't stopping on the transmissions from the other
department in the neighboring county.

It's also very helpful on the low VHF band where tropo ducting brings
in low-band fire comms from clear across the state at night. Great if
I want to DX the low VHF band, I can just turn CTCSS off, but if I
want to take a nap and only have the scanner wake me up if there's a
fire here in town, I can set CTCSS on and the scanner will only go off
if the local fire companies become active on the air.

In summary, CTCSS is certainly not required to hear anything, but it
can sure come in handy to have this feature on your scanner.

Finally, I note that the original poster's address included a ham
callsign, so I will note that most VHF/UHF repeaters nowadays are
using CTCSS on the input side at the very least, whether they
retransmit the tone or not, and so amateur radio gear for the 2m and
440 bands pretty much must be equipped with CTCSS encode at least,
unless you want to be limited to using the rig only on simplex.

CTCSS is also often referred to as PL (for Private Line, Motorola's
trademark for its implementation of CTCSS on its commercial
transcievers), and also as CG (for Channel Guard, which is General
Electric's name for the same technology).

Hope this helps!

John D. Kasupski, Tonawanda, NY, USA
Amateur Radio (KC2HMZ), HF/VHF/UHF Monitoring (KNY2VS)
Member ARATS, ARRL, WUN

Rick wrote:

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


Excellent response Rick!

Thanks,

-Donald
--
"One ought, every day at least, to hear a little song, read a good poem,
see a fine picture, and, if it were possible, to speak a few reasonable
words." - Johann Wolfgang von Goethe

When I used to work as a courier, our Yaesu and Midland radios had a
"Tone" switch on them. When the tone was off, I could hear all the
other users on same frequency. However, of course, when the tone was
on, only our company could be heard. When I monitor the courier
company I used to work for, with my scanner that is not CTCSS
equipped, I will hear all the other users on that frequency.
Fred Burgess
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.