Different Input and Output tones

[JRichard]

My City's local PD uses two repeaters, simulcasted, to cover a large area. Amalgamated two municipal forces into one so their assets came with them.

Interesting thing about is they use two different output freqs and two different output tones.

Example:

153.830 DC 125
154.770 CT 127.3

Another interesting characteristic is the input tone to both repeaters is 155.490. A PL tone of 127.3 is being transmitted but no DPL tone. I've read something about Tone translation. Does the PL input and DPL output apply here?

I know very little about radio systems. Is it simply that the 153.830 repeater doesn't require a DC tone to activate it? Or is the repeater activated another way?

Anyway, just wondering is all.

 

[ofd8001]

I am unaware of any repeater, or radio for that matter, that is capable of sending more than one PL or DPL tone.

PL and DPL tones are like gate-keepers, who keep undesirable things outside. They only allow a signal with the correct tone to pass beyond a certain point in a radio, thus alleviating a listener from hearing stuff he really isn't interested in hearing.

What I suspect is happening, is that the police officer will have to select which of the two repeaters he wants to use, based upon his location.

In our fire radio system, we have an area of the county where the main system has a "hole". To fill the hole in, a separate repeater was installed in that area. The firefighters have to turn their radios to the frequency that the fill-in repeater is listening to. The output side of the repeater is the same as the main system.

That's sort of similar to what's going on in your place, the radio user has to know which site he wants to use. It can be likened to car transmissions. Most are automatics, but you have a manual shifters out there too.

 

[KW4EZR]

The Police Dept. here uses a repeater with two different PL tones.

465.475 PL131.8 input
460.475 PL127.3 output

Also have a local Amature repeater that uses two PLs

144.530 PL 100.0 input
145.130 PL 156.7 Output.

SO it does happen, but I have never seen one PL and one DPL.

 

[CCHLLM]

I'm confused (nothing new about that). 153.830 and 154.770 are mobile frequencies, not repeater output frequencies, though I suppose anything's possible with every Barney, Goober, Gomer, and Aunt Bea in the coordination business. Do you mean that the repeater output frequency is 155.490 with 127.3 PL for both repeaters, and that one repeater uses 153.830 DCS 125 for its input, while the other uses 154.770 PL 127.3 as the input? If so, that's a fairly common practice for multiple repeater sites that are not "steered" or simulcast. Most, however, use the same frequency for the repeater inputs but use a different subtone. There are quite a few around that use split subtones combos of digital and analog subtones. And yes, the user has to select the repeater he/she needs to use in the cases where there is no steering or simulcast going on.

 

[SCPD]

The Inyo County, California Sheriff's Department uses two different repeater pairs and each has output tones which differ from the input tone. There are a few 6 meter ham repeaters in the west which use different tones between output and input. I just finished programming the 6 meter frequencies in my Yeasu FT-8900 and came across this. Unfortunately the radio will not accept different output/input tones. It's a good thing I have plenty of memory so I could program the same frequency again with tone decode using the ouput tone. That won't help when I'm on manual using the channel with the correct input tone. I have the channel I transmit on programmed for encode only. Since 6 meters is subject to skip (not much at all right now, but wait for the next solar maximum) it is good to have an output tone, something which is rare on amateur repeaters, so you can narrow down what repeater you are actually hearing.

For the scanner user the input tone differing from the output is not of too much concern. We normally only listen to the output frequency and the tone that on it is the most useful to us. Unless you are in a situation where you can't hear the repeater but have nearby mobile units you want to listen to. Of course in this case you would only hear one sided communications when mobiles are talking with dispatch.

 

[Voyager]

My City's local PD uses two repeaters, simulcasted, to cover a large area. Amalgamated two municipal forces into one so their assets came with them.

Interesting thing about is they use two different output freqs and two different output tones.

Example:

153.830 DC 125
154.770 CT 127.3

Another interesting characteristic is the input tone to both repeaters is 155.490. A PL tone of 127.3 is being transmitted but no DPL tone. I've read something about Tone translation. Does the PL input and DPL output apply here?

I know very little about radio systems. Is it simply that the 153.830 repeater doesn't require a DC tone to activate it? Or is the repeater activated another way?

Anyway, just wondering is all.

Cross-tone (AKA tone translation) or tone-code is not common, but it does happen. DPL is just a different form of CTCSS. Perhaps they couldn't find a 'free tone' so they used a CDCSS code instead.

Joe M.

 

[kb2vxa]

Hi all,

Very few repeaters pass tones through a channel separate from voice, (which has certain advantages) most generate thier own tones or codes. This means the input may be one thing and the output quite another, PL, DPL or whatever. There's more to a repeater than meets the eye and it's called a controller.