Tone Data & Squelch Question

[Cbandguy]

I have the Uniden 780 XLT base scanner. Works great and I love it! Can someone explain to me exactly what the purpose of the squelch mode and tone data features are for? Although I read the manual, I still don't understand the benefit or advantage that you get by activating them. My scanner works great and receives sensitive signals without activating. What benefits would I find by activiating this feature?

Why do some frequencies have a pre set sub audible tone and what purpose do they serve? Is there an advantage to using a frequency with a sub audible tone or not using a sub audible tone if the frequency has one? Why do some frequencies not have a sub audible tone?

 

[K5MAR]

I have the Uniden 780 XLT base scanner. Works great and I love it! Can someone explain to me exactly what the purpose of the squelch mode and tone data features are for? Although I read the manual, I still don't understand the benefit or advantage that you get by activating them. My scanner works great and receives sensitive signals without activating. What benefits would I find by activiating this feature?

Why do some frequencies have a pre set sub audible tone and what purpose do they serve? Is there an advantage to using a frequency with a sub audible tone or not using a sub audible tone if the frequency has one? Why do some frequencies not have a sub audible tone?

Carrier Squelch mode is just like most scanners on the market, any signal on a frequency will stop the scan and be heard on the speaker, as long as it's strong enough to open the squelch.

Tone Squelch uses the CTCSS/DCS code (if present) to "filter" the received signal on a given frequency. CTCSS = Continuous Tone Coded Squelch System, a subaudible tone sent with the transmitted signal. DCS = Digital Coded Squelch, a digital signal sent with the transmitted signal. These are commonly used to control access to a repeater, if the received signal doesn't have the proper CTCSS/DCS code, it will not be repeated. The Motorola trademarked terms for these are PL (Private Line) and DPL (Digital Private Line).

The presence of these tones can be used to limit what stations you hear on a particular frequency. Say the frequency of 460.500 MHz is used by two different agencies in your area, and you only want to listen to one of them, you would input the CTCSS/DCS code for that agency in the proper chanel on your scanner. Then the scanner will skip transmissions that don't have the proper tone.

Not all agencies, especially those on simplex freqs, use CTCSS/DCS codes. And not all the proper tones have been submitted to the RR database. The BC 780 and it's siblings have the ability to decode and display the tone being used. But they're not as fast at this as the Pro-92/2067 scanners from Radio Shack.

Any questions? Then close your book (er, computer screen), and take out a blank sheet of paper for a pop quiz! :lol:

Mark S.

 

[JoeyC]

www.google.com

use it for everything...

 

[Cbandguy]

If I understand this correctly, you are saying that the main benefit of coding a tone on a frequency is to narrow down the signal you receive to your local area if you are receiving more than one signal from another area and to prevent that distant signal on that same frequency from being received?

 

[K5MAR]

If I understand this correctly, you are saying that the main benefit of coding a tone on a frequency is to narrow down the signal you receive to your local area if you are receiving more than one signal from another area and to prevent that distant signal on that same frequency from being received?

Yes, that is one reason, and the main one for most. Another use would be to ID two separate users of the same frequency. If town A and town B both use the same freq, but with different PL tones, and your scanner supports both CTCSS (PL) and alpha tags, you could put the freq in two different channels with the different tones along with the appropriate alpha tag. Then you wouldn't have to guess which one was talking, the display would tell you. Of course, as you gain experience you'll learn to tell different users apart just by the way they sound, but until then, using the tones to seperate them is a good way to start.

It also helps reduce skip interference, as long as the skip signal doesn't have the same tone as the local agency!

But just to clarify, using CTCSS/DCS doesn't "prevent" a signal from being received, it stops the squelch from opening and causes the scanner to resume scanning.

Mark S.

 

[BoxAlarm187]

K5MAR has done a great job of explaining how PL/DPL works, and I thought that I might throw my $0.02 in about them.

I live in a rural/suburban area, and have my antenna at 50' on the side of my house. Since this is the case, I usually have the luxury of picking up multiple jurisdictions on the same frequency. If I DIDN'T use PL's on the freq's, I'd have to sit and listen to the freq to determine who it is.

However, by using the PL or DPL, I'm able to determine exactly who is on that freq, and put the appropriate alpha-tag on the screen. This allows to to give a quick glance at the screen and see who's yapping.

 

[Cbandguy]

Thanks a bunch for all your responses. I too have a house roof mounted scanner antenna and because I pick up such strong signals from all over my area and beyond, I tend to pick up double or triple services on one particular frequency causing much confusion in identifying the actual service that I'm receiving. I never really programmed these frequencies into my scanner more than once but with your valuable input, I now realize that this is a feature that can be fully utilized and I know my scanner will offer these features. I'll now be off to my scanner for some serious frequency programming! :lol:

 

[nyscan00]

Try this site:
http://www.bommeltje.nl/scanners/english/wintone.shtml

 

[rdale]

Wintone is not needed for DCS/PL tones unless your scanner can't.