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Old 05-18-2017, 9:47 PM
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Default Patched TGs

Question:

I notice a-lot of patches on my local P25 system. Even though I have only one talkgroup in a scanlist, I of course will get all the patched traffic. Thing is, the scanner shows the "patch" indication AND the patched talkgroup ID. Is there some way to have the scanner only pass the TG I programmed and not any patched TG. The scanner obviously knows the patched TG number, can it not be used as the filter?

I say this as the County is so disrespectful of scanner users (hahaha) by often patching through TAC groups that are encrypted. So I get a lot of "stops" on traffic I don't care about/can't hear. So I then miss "real" traffic while it's stopped unnecessarily.

Possible? Enhancement request?
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Old 05-19-2017, 12:17 PM
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No. The calls are broadcast to both talkgroups. It's either all or none. If you look at the control channel log, you can learn more about the commands that are sent to the radio. The only way might be to limit your list to specific Radio IDs.

It's something like this:

CC says: if you are affiliated with talkgroup 1 and/or talkgroup 2, you need to tune to voice channel 2 and receive the broadcast.

It's not: Hey so and so on talkgroup 1 is calling and you are on talkgroup 2, so you need to listen to this voice channel, because you are patched in.

The patch is the audience not the source.
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Old 05-19-2017, 2:10 PM
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P25 isn't normally used here in europe. I think there is only one system, in poland, so I don't know anything about it. But other Motorola system and Tetra are doing this when patching TGs:

If TG1 are patched to TG2 the system sends out periodicly and when affiliating that TG1 and TG2 are now converted to TG32000.
No calls are broadcasted to TG1 and TG2 and are only received from TG32000.

/Ubbe
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Old 05-19-2017, 8:02 PM
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I've heard it said that many US army bases in various European countries use P25.
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Old 05-19-2017, 10:20 PM
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I think there may be some confusion. I get how patching works but what I'm seeing is:

Say I'm monitoring TG 0001.
The TG is patched with TG 0002 by the TRS at such and such time.
When a call on TG 0002 comes in, my scanner reads "Patch" and displays 0002 (not 0001).

Since the scanner obviously can see the 0002 is the "real" TG being sent down from the CC is sending it down as part of the patch, it should be able to ignore it since I'm not "scanning" for it even though 0001 is also in the patch.

Make sense?
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Old 05-19-2017, 10:45 PM
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The control channel is doing one of two things:

Sending commands for radios assigned to either talkgroup to tune in.

Or creating a third talkgroup, which the radios are told to temporarily tune into when it is active.

The call is on the patch. The audience is the patch. It's either listen to call broadcast to the patch audience or listen to no call at all.

Watch the CC stream on DSD+ sometime.
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Old 05-19-2017, 11:24 PM
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Quote:
Originally Posted by mejnetguru View Post
I think there may be some confusion. I get how patching works but what I'm seeing is:

Say I'm monitoring TG 0001.
The TG is patched with TG 0002 by the TRS at such and such time.
When a call on TG 0002 comes in, my scanner reads "Patch" and displays 0002 (not 0001).

Since the scanner obviously can see the 0002 is the "real" TG being sent down from the CC is sending it down as part of the patch, it should be able to ignore it since I'm not "scanning" for it even though 0001 is also in the patch.

Make sense?
There is no way to differentiate and pick out the traffic like you are suggesting. When the system patches TGs, the CC message tells all of the radios to use a specific TG (such as TG 2 in your example). This means that all radios that were set to use TG 1 will now use TG 2 for all transmissions for the duration of the patch.

The scanner is showing the patch message to let you know that it is monitoring a different TG because it recognizes that the TG you are listening to has been patched to a different TG. There is no way for any scanner, or an actual system radio, to know what TG the radio was originally set to. That would kind of be counterproductive to why they were patched in the first place.

For example:
Radio A is set to TG 1.
Radio Z is set to TG 2.
  1. Radio A talks on TG 1.
  2. Radio Z talks on TG 2.
  3. TG 1 is then patched to TG 2.
  4. Radio A talks on TG 2.
  5. Radio Z talks on TG 2.
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Old 05-20-2017, 1:29 AM
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Quote:
Originally Posted by BrianG61UK View Post
I've heard it said that many US army bases in various European countries use P25.
Correct..Most of them using P25.
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Old 05-20-2017, 10:43 AM
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Not just European, but world wide for the P25 usage.
Even the USSS with POTUS, uses P25 when OCONUS


Quote:
Originally Posted by BrianG61UK View Post
I've heard it said that many US army bases in various European countries use P25.
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