Repeater With 2 PL or DPL codes

[VolFirefighter911]

I have 2 agencies in my area that have repeaters with different PL or DPL codes on the input and output sides. One PD uses 179.9 on the input and 162.2 on the output. One FD uses DPL 243 on the input and DPL 131 on the output. Is this common? What are the advantages or disadvantages? Why do the tones on the input side not bleed over to the output and cause two tones to be present on the repeater output?

[HumHead]

There are probably several possible reasons for running different tones on the input and output:
1) To provide some small amount protection for the system by making it a little more difficult for clowns to jam up the system by putting the input into their illegally modified ham HT. If they just put it in with the output tone, they don't bring up the repeater, and frequently move on to amuse themselves with the local McDonalds drive through instead.
2) Due to co-channel users, the same tone is not available on both the input and output frequencies.
3) The "Poor Man's Voter". I am aware of several agencies who get wide area coverage by putting up multiple repeater sites with the same frequency and ouput PL. Each repeater, however, uses a different input PL, so users pick the closest machine by changing their TX channel to one with the correct TX tone for their local repeater.

Most (properly aligned) repeaters are set up so that the received tone is stripped from the audio before it is passed to the transmitter. This allows the repeater to "regenerate" a clean PL signal, strip the PL, or TX with a different PL.

[Jim202]

There are probably several possible reasons for running different tones on the input and output:

Sometimes the radio shop will do this in trying to be smart and complicate things. Another reason is sometimes a repeater has desense and will lock up the repeater with the same tone on both the in and out. Some sharp radio techs will put a different tone on the output to make the repeater shut down when the input tone goes away.

I would rather see the sharp radio techs fix the problem rather than mask it. But then again, maybe they don't know how.

Not knowing just how this repeater is functioning, these are the best ideas that seem to come to mind. You would have to provide more input for the rest of us to second guess why the repeater system is set up the way it is.

Jim

[n9upc]

Are you sure that there is only one repeater on that freq in the area in use by the PD and FD.

One of the counties I use to be an EMT in had a North and South repeater. They had the second repeater donated so what they did was put up the second repeater with a split PL.

Example North was 146.2 in and out for a PL, and the south was 118.8 in and 146.2 out. This way no re-licensing for freqs was required. Now both repeaters cover the county but the problem was the rx of the repeater.

So now people can talk to one another using different repeaters but to the scanner listeners and users there is no difference.

[bernie]

My two bits worth:
"Cross codes" In with one, out with the other.
This is a very common practice when one has several sites on the same frequency.
I have several repeaters on 462.625 on this island, each with a different input PL, out on 1A.

[nmfire10]

As I was told when I asked someone why... "It keeps out most of the Touch Tone Terrorists.

I didn't do this with the new system we have going in. I am going to monitor it and if I see idiots having fun with their modified ham radios, I'll do it. It will probably keep MOST of them out but it is not fool proof.