BCD996P2: P25 Transmissions Often Start With A Burst Type Noise

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So how come when listening to P25 trunking, the beginning of transmissions sometimes starts with what sounds like a short quick analog-style squelch tail noise? BURP!!! It actually happens right at the beginning of the transmission right when the user first keys up. It doesn't happen all the time, but it happens a lot. It never occurs on DMR, only P25. Why? Is there a way to get rid of this? It's annoying.
 

jonwienke

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If you have the channel programmed as conventional, it sometimes takes the scanner some time to realize that it is receiving digital rather than analog FM. When that happens, you'll hear some digital static before it starts decoding the bits into audio.
 

jonwienke

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Check your programming. The scanner isn't assuming digital for whatever reason, and is playing the transmission as analog FM occasionally for a brief moment until it detects that it needs to decode digital audio.
 
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Well, I just have it programmed as a P25 Trunking system type. Is that enough for the scanner to know its digital from the getgo, or are there other settings to program?
 

GTR8000

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Check your programming. The scanner isn't assuming digital for whatever reason, and is playing the transmission as analog FM occasionally for a brief moment until it detects that it needs to decode digital audio.
He already stated that this is a P25 system, so your reply makes no sense. There are no settings in the 996P2 that would allow the scanner to not "assume digital" for that system type. P25 is all digital, all the time, period.

You seem to be confused, and must be thinking of a Motorola Type II system, which can have a mixture of analog and digital talkgroups. There is a P25 Wait Time setting for that type of system, but not for P25 Standard.
 

adcockfred

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Your player sounds like it is struggling from the get go. So there are many things it could be. How high is your sample rate?
 
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What "player" do you mean? This is a sound that the scanner makes at the beginning of transmissions.
 

garys

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I don't know what software you are using, but on ARC996XT, you can set the audio type for the talk groups to "Analog", "Digital" or "All". Check on your scanner (or software) to make sure that you have Digital selected. That might do it.

Also, digging a bit deeper, I see that most of the county is still on the EDACS system. If there is any patching from the EDACS system to the P25 system, there might be some sort of "hash" at the start of transmissions.

Just a couple of things to think about.
 
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Well, this is a P25 Phase 2 system (not Type II as in older Motorola systems). Most of the talk groups are Phase II now, but there used to be more Type I activity. For some odd reason, sometimes talk groups on this system will switch back and forth between Phase 1 and 2.

But I'm not sure that's the issue here. And I don't think the software has any effect. It's the scanner itself that makes this noise. I use ProScan, but even without the software running, the scanner still does the same thing.
 

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The scanner isn't immediately interpreting the broadcast as P25 digital, so sometimes you're getting a short blip of digital noise at the beginning of transmissions. Why, I can't tell from the recording. I sometimes hear something similar when getting Close Call hits from a P25 site, and the scanner has to figure out whether the signal is analog or digital. The scanner shouldn't have to do that if the system is programmed as P25, unless there is a firmware bug.

Is the talkgroup in the recording Phase I or II? How strong is the signal?
 
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Yes, I have it programmed as a P25 trunking system. The signal strength is full scale. All the signal bars on scanner are lit up. This is a simulcast system that I have to use a yagi on in just the right sweet spot with a TV attenuator.
 

garys

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They switch back and forth because Phase 2 systems are backwards compatible with older Phase 1 radios. If a Phase 1 radio affiliates with the system, I think all of the radios on that TG drop back to Phase 1.

I mentioned the software, because if the software was set to "ALL", that's how the scanner is programmed. If you want to just look at the scanner, you can do that too, but it might be easier to see how the programming is set in the software.

Well, this is a P25 Phase 2 system (not Type II as in older Motorola systems). Most of the talk groups are Phase II now, but there used to be more Type I activity. For some odd reason, sometimes talk groups on this system will switch back and forth between Phase 1 and 2.

But I'm not sure that's the issue here. And I don't think the software has any effect. It's the scanner itself that makes this noise. I use ProScan, but even without the software running, the scanner still does the same thing.
 
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Set to all what? I don't see anything in ProScan that says "ALL" where I've got this system programmed. This system is simulcast, unfortunately.
 

jonwienke

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That could be the problem--the scanner struggling with the simulcast and not immediately identifying the signal as digital.
 
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