Ltr System @ tones

[Saint]

I listen to a LTR STANDARD System, and have noticed that when I do conventional frequency searches for new frequencies some of the frequencies in the LTR System have ctcss and dcs tones comming up with some of the LTR Frequencies. Is this normal that LTR frequencies also have ctcss and dcs tones for conventional modes.
Steve

[KCChiefs9690]

They don't actually have tones, the scanner just thinks that they do. It could be some interference that the scanner is picking up and interpreting as tones, even though there are none in an LTR system.

Hope this helps,

[richrowl]

A frequency is merely a frequency and perhaps is being used in a conventional mode and not in an LTR mode.

[Saint]

Originally Posted by KCChiefs9690

They don't actually have tones, the scanner just thinks that they do. It could be some interference that the scanner is picking up and interpreting as tones, even though there are none in an LTR system.

Hope this helps,

Thanks KCChiefs9690, it's the first time I came across this, I was just wondering.
Steve

[dtscho]

It could be a situation where the same frequency is used as part of an LTR system, and is also used as a conventional channel with a CTCSS/DCS tone.

Dave

[bc780l]

LTR systems do indeed have tones. Since there's no control channel, the control information is sent as data via CTCSS tones. I've not seen any DCS used, but likely someone is now doing it. There's a standard set of tones used for the control information. It was initially set at 150Hz. Initial communications handshakes take place as well as continuous exchange of data via this subaudible channel during conversations between the repeater and the mobile units to ensure that mobiles are accessing only authorized systems and to see what repeaters are available. Voila--no dedicated control channel! Uniden Commerical also has an enhanced LTR protocol called Extended Sub-Audible Signaling (ESAS) which allows radios to be uniquely identified and allows "roaming" between different LTR systems. When listening in on an LTR system using conventional mode vs LTR trunking mode, you may indeed notice the tones and wonder ... but again, it may also be an adjacent system, as mentioned above.

[DaveNF2G]

Important note: CTCSS != subaudible datastream

[bc780l]

Yep. Datastream--modulated or unmodulated (regarding data content--obviously if a tone is present, it's "modulated" but not talking about that here). CTCSS is a continously transmitted subaudible tone, with no internally modulated data. DCS is continuously modulated subaudible data that uses a 134.3Hz tone as a bit timing rate. DCS sends a standard 23 bit asynchronous datastream, LTR sends several types of a longer, continuous, synchronous datastream using a subaudible tone base. They're all related and it sounds like a tone on the signal--which indeed it is--but it's used differently in different systems.

[grem467]

keep in mind that some LTR controllers can also be set up to use PL/DPL at the same time, making the channel available for conventional use when a trunked user does not need it.

This is a good use for a single channel LTR system where the goal is to use it as a community repeater.