Conventionally scanning simulcast p25 voice chs sounds bad

[billy2047]

Hi all, does anyone know what causes XTL/XTS radios to sound bad conventionally scanning simulcast P25 phase 1 voice CHs?

By sound bad I mean audio comes through like microphone is underwater, skipping/mumbling words etc.

However, all sounds fine using NAS method

Radios are set to CQPSK and Digital CSQ under ASTRO tab in the conventional personality.

Thanks all

 

[ElroyJetson]

C4FM is required for linear simulcast. CQPSK is susceptible to simulcast distortion. There you are.

What is the difference between C4FM and LSM Modulation for P25? | Tait Communications Blog

Simulcast networks are used by a third of US Public Safety Agencies. Read more about the two most common types of simulcast modulation.

blog.taitcommunications.com

 

[KevinC]

C4FM is required for linear simulcast. CQPSK is susceptible to simulcast distortion. There you are.

What is the difference between C4FM and LSM Modulation for P25? | Tait Communications Blog

Simulcast networks are used by a third of US Public Safety Agencies. Read more about the two most common types of simulcast modulation.

blog.taitcommunications.com

Uh...no.

 

[billy2047]

C4FM is required for linear simulcast. CQPSK is susceptible to simulcast distortion. There you are.

What is the difference between C4FM and LSM Modulation for P25? | Tait Communications Blog

Simulcast networks are used by a third of US Public Safety Agencies. Read more about the two most common types of simulcast modulation.

blog.taitcommunications.com

The thing is if I set it to C4FM radios won't even unmute.

 

[wgbecks]

Your post was a little ambiguous. If scanning a conventional P25 simulcast then go to the Astro Tab in the associated Conventional Personality
and set the Digital Modulator Type to CQPSK. If you're scanning (NAS) a P25 Simulcast TRS, go to the Digital Tab in the Trunking System and
set the Digital Modulator Type to CQPSK.

If that doesn’t fix the problem then perhaps the radio alignment needs to be checked.

 

[ElroyJetson]

I kind of got that backwards. C4FM is not the mode you want to use.

From RR's own page on it:

Simulcast Distortion - The RadioReference Wiki

wiki.radioreference.com

 

[billy2047]

If radios need alignment then how do they all sound fine using NAS? Are there two receivers in XTL/XTS?

 

[KevinC]

I agree, the radio probably needs to be aligned. It should unmute if set correctly and using C4FM, if it's within alignment requirements.

KevinC, I'm quoting from the Tait site. How is that wrong?

You absolutely DO NOT use C4FM for LSM...ever,

 

[ElroyJetson]

Yeah, I got that backwards...I read it correctly, but got phrases transposed. Oh the fun of getting older!

 

[KevinC]

Try setting the channel(s) to wide-band (20 or 25 kHz) and see how it sounds.

 

[wgbecks]

....... XTL/XTS radios to sound bad conventionally scanning simulcast P25 phase 1 voice CHs?

Are you saying that you’re just scanning the same voice trunk channel frequencies as those associated with the Phase 1 TRS that sound
find when uisng NAS method or are you scanning some other P25 system?

 

[billy2047]

I'm "just scanning the same voice trunk channel frequencies as those associated with the Phase 1 TRS" and yes it sounds fine using NAS

 

[GTR8000]

The obvious question would be...if it works fine using NAS, why bother scanning them conventionally? No need to answer that, we all like to experiment from time to time, but I had to ask.

Is this the Volusia County system, or some other? Are you certain that the site you're scanning is a simulcast cell as opposed to a standalone site? That will make a difference in the selection of C4FM vs CQPSK (although CQPSK will still work on a standalone site, perhaps not ideally, but it won't be a show stopper). And you're certain that all of the frequencies are entered correctly and are set to 12.5 kHz modulation, which is what P25 uses?

What happens if you simply park on a single traffic channel with scan off? Same lousy audio?

 

[wgbecks]

I'm "just scanning the same voice trunk channel frequencies as those associated with the Phase 1 TRS" and yes it sounds fine using NAS

I setup one of my XTS5000 that's is normally used for NAS to replicate your setup by dropping the same list of voice trunk channels
into a separate zone using a single receive only "Astro" personality and with the channel bandwidth set to 12.5 kHz as it should be
for a P25 emission. The verdict? No distortion, clean audio in NAS as well as conventional P25 scanning.

Are your conventional personality(s) setup for Astro or Mixed Mode? It's possible in Mixed Mode and Non-Astro to enable Hear Clear,
but I don't think the compandor would be active during a digital call. Are you absolutely sure your voice trunk frequencies as programmed
are correct?

 

[billy2047]

The obvious question would be...if it works fine using NAS, why bother scanning them conventionally? No need to answer that, we all like to experiment from time to time, but I had to ask.

Is this the Volusia County system, or some other? Are you certain that the site you're scanning is a simulcast cell as opposed to a standalone site? That will make a difference in the selection of C4FM vs CQPSK (although CQPSK will still work on a standalone site, perhaps not ideally, but it won't be a show stopper). And you're certain that all of the frequencies are entered correctly and are set to 12.5 kHz modulation, which is what P25 uses?

What happens if you simply park on a single traffic channel with scan off? Same lousy audio?

I'm doing it for kicks and giggles .

It's some random 3 frequencies (2 voice CHs) simulcast phase 1 sys and all freqs are correctly entered with 12.5k mod.

If I park on a single traffic channel with scan off, same lousy audio. It sounds exactly like cheap SDR dongle decoding simulcast system with skipping words, bits and pieces of words that are broken.

 

[billy2047]

I setup one of my XTS5000 that's is normally used for NAS to replicate your setup by dropping the same list of voice trunk channels
into a separate zone using a single receive only "Astro" personality and with the channel bandwidth set to 12.5 kHz as it should be
for a P25 emission. The verdict? No distortion, clean audio in NAS as well as conventional P25 scanning.

Are your conventional personality(s) setup for Astro or Mixed Mode? It's possible in Mixed Mode and Non-Astro to enable Hear Clear,
but I don't think the compandor would be active during a digital call. Are you absolutely sure your voice trunk frequencies as programmed
are correct?

is your system simulcast?

 

[billy2047]

I've also notice that with my XTL/XTS (havent try APX yet), I'd get slightly more range scanning trunked freqs conventionally compare to using NAS method, hence why I wanted to do that

 

[wgbecks]

is your system simulcast?

Yes.

 

[chrismol1]

I've also notice that with my XTL/XTS (havent try APX yet), I'd get slightly more range scanning trunked freqs conventionally compare to using NAS method, hence why I wanted to do that

Try knocking down the RSSI thresholds lower, RSSI Acceptable and RSSI Good under Trunking Configuration

 

[chrismol1]

Have you done a firmware upgrade? (Don't laugh, that is Motorolas answer for everything) Or if so maybe try doing it again simply rewrite the latest firmware