P25 Audio

[Stick0413]

My experience is it depends on the system for P25. With analog you know what to expect and it will be close to that. With P25 you can get some great sounding systems (and freqs for the non trunking P25) and some that sound like complete crap. Overall in my area the digital sounds great.

 

[tampabaynews]

I agree on the notion it really depends on the system.

For example, in my area, an airport PD is on a conventional P25 system operating on 400mhz, and they sound great! I can be over dozen miles from the airport and they are crystal clear with 1 bar.

However, a much larger county 800mhz trunked P25 system... sounds like garbage.

 

[Gezelle007]

I agree on the notion it really depends on the system.

For example, in my area, an airport PD is on a conventional P25 system operating on 400mhz, and they sound great! I can be over dozen miles from the airport and they are crystal clear with 1 bar.

However, a much larger county 800mhz trunked P25 system... sounds like garbage.

I bet that's because the county system is probably simulcast, those systems tend to sound like crap when you get too far away, even when you are picking up the strongest repeater signal. At least that is how it sounds for me when I get too far away.

Id like to get a new digital scanner for Christmas this year, see If I cant put something in that is local and p25.

 

[tampabaynews]

I bet that's because the county system is probably simulcast, those systems tend to sound like crap when you get too far away, even when you are picking up the strongest repeater signal. At least that is how it sounds for me when I get too far away.

Id like to get a new digital scanner for Christmas this year, see If I cant put something in that is local and p25.

It even sounds bad when I'm in within the county where the system is deployed.

 

[w2csx]

with a well designed network P25 will preform at least equally well if not better than analog.

I guess if this is the case,why switch to a p25 system?

 

[TrenchFeeder]

Its almost like comparing it to newer HD TV's vs the older. If you go in to Frys or Best Buy or something and check them out, they are so high definition and clear that its TOO clear. The movement is to fluid. Its so real looking that it looks fake.

off topic, but my friend just bought a new 3D TV it looks great, however it makes all movement look ultra smooth and looks sped up and somehow makes everything you watch look like a soap opera.

 

[Gezelle007]

off topic, but my friend just bought a new 3D TV it looks great, however it makes all movement look ultra smooth and looks sped up and somehow makes everything you watch look like a soap opera.

Yeah exactly haha, I have an older HD tv from Sony and it doesn't make things look like that, I also have a blu ray player and it also doesn't have that effect, it was only recently that I noticed it was the actual TV's that have that kind of look.

 

[hitechRadio]

I think you will find that the difference between your old analog system and your new digital system is location, location, location. Your analog system probably had only one base station/repeater. Your new digital system will have a number of stations, all interconnected with each other and your dispatch You might even have one at the jail. If your analog system had been engineered and installed the same way, it would OUT PERFORM the digital system.

Digital has one drawback that it will NEVER be able to overcome, there isn't any redundancy to the information it transmits. Forward Error Correction (FEC) is not the same as redundancy. If you loose 50% of the transmission with digital, you don't have ANY communication. Analog can give dependable communication and still loose over 80% of the transmission.

Are you serously going to assume that he has a different system design compared to analog because he is digital. Digital can and will outperform analog.


I use and listen to P25 radios everyday, I have gotten to the point where I cannot even listen to analog anymore due to the hisses and scratches.

It must be something with scanners I guess, I do not have a p25 scanner to compare, But the audio sounds excellent on my XTS2500. Some users are using Efjohnson p25 equipment , and for some reason there audio does not sound near as good as the motos do on transmit.

We have done comparisons, same antenna and a quantar programmed mixed mode analog and digital, the digital smoked the analog hands down. We have done the same thing with Mototrbo same result.

 

[jackj]

Try reading what I said hitechradio. One repeater location vs 10 through out the county. Ten miles from the repeater vs a few hundred feet. There is a reason why analog systems don't usually have multiple repeaters -- -- THEY DON'T USUALLY NEED THEM! While digital system do usually need them.

Please note the use of the work "Usually"

 

[hitechRadio]

Try reading what I said hitechradio. One repeater location vs 10 through out the county. Ten miles from the repeater vs a few hundred feet. There is a reason why analog systems don't usually have multiple repeaters -- -- THEY DON'T USUALLY NEED THEM! While digital system do usually need them.

Please note the use of the work "Usually"

I did read it several times,,,What you are saying is simply not true, Period.

Like I said earlier,, We have done comparisons, same antenna and a quantar programmed mixed mode analog and digital, the digital smoked the analog hands down. We have done the same thing with Mototrbo same result.

One reason you may have more digital sites than the previous analog system, is one it is much easier to implement multiple sites in a digital simulcast and/or multisite system compared to analog. Another thing is when alot of older analog systems were or should I say if they were enginerred, it probably was engineered for mobile's, most new systems are being engineered for portable's.

The reason I believe you have never have even used a digital system, or you would not be saying what you are saying. I'm not trying to single you out, and I apologize. It does not matter if it was P25, NXDN, Trbo, IDAS or any of the other digital formats. The audio between the formats may sound a little different but all will match or exceed analog rf wise.

Ask your self this question, y would anyone want to go digital if what you say was the case. I would be the first to say digital sucks,, but it is simply not true, digital, as far as rf coverage, excellent:Fact. digital, as far as audio, excellentpinion.

 

[JRayfield]

I have no personal experience with P25 in an operating system. I do have a lot of experience with MOTOTRBO, so I know how much better MOTOTRBO works, as compared to analog, in providing additional coverage.

I have seen some state the P25 systems, given the same antenna height, power output, receiver sensitivity, etc., will have slightly less range than analog systems (likely, comparing to wideband analog). On the other hand, I've seen some state, as you do, that the range of P25 systems is better than analog.

I asked one dealer, who has installed and services both P25 systems and MOTOTRBO systems, if the P25 radios tend to require a bit higher signal level for 'recovered audio', as compared to MOTOTRBO. He said 'yes', that is the case.

What is your opinion on this, since you have worked with both types of systems, too?

John Rayfield, Jr. - CETma

 

[hitechRadio]

When I had tested the systems, it was not at the same time. As we where comparing Analog to digital, not Trbo vs P25. That said, if there was a difference I would not have been able to tell, my opinion of course. If i have a chance to test again I will compare them, know you got me curious. I wish my monitor had DMR test, so I could compare on a monitor.

 

[Baylink]

Hitech, and JackJ: you guys are having two different conversations.

In the final analysis: analog audio can be better than digital audio -- if the users are on the same block. Digital signals will stay nearly perfect much farther than analog will... but then they'll "fall off the cliff", and you won't have *anything at all* -- in a situation where, with some work, you might still be able to communicate using analog radios, if you worked at it hard enough.

Whether this is an acceptable trade off depends on what you're doing.

 

[jackj]

Baylink, you are right. HiTech twists what I post into something different and then complains that I don't know what I'm talking about. Most of what he accuses me of has no bases in what I posted. I'm done with the discussion as he appears to be someone who just wants to argue.

As for the question of "Which is better", it depends on what you are trying to do. If you are only interested in voice communications then analog is better. But if you want to integrate voice with control and data channels then digital is better. But, like I said, this is my last post on the subject. Bye all!!! Happy New Year!!

 

[hitechRadio]

I do not know how I am twisting anything, I was just staing the fact that you should not assume that he has a different system design cause he went digital.


Here is what was said....
--------------------------------------------------------------------------------

Quote:
Originally Posted by canav844
Our officers went from having to get into their squad and drive out of the jail sally port to get their mobile to reach our repeaters to being able to get in through their portables, it all comes down to system design and I've seen analog out reach digital and digital outreach analog, it's still a matter of RF getting from point A to point B.

Response by Jackj

I think you will find that the difference between your old analog system and your new digital system is location, location, location. Your analog system probably had only one base station/repeater. Your new digital system will have a number of stations, all interconnected with each other and your dispatch You might even have one at the jail. If your analog system had been engineered and installed the same way, it would OUT PERFORM the digital system.

Digital has one drawback that it will NEVER be able to overcome, there isn't any redundancy to the information it transmits. Forward Error Correction (FEC) is not the same as redundancy. If you loose 50% of the transmission with digital, you don't have ANY communication. Analog can give dependable communication and still loose over 80% of the transmission.
_______________________________________________________________________________________________________________________



As far as the last paragraph concerning Redundancy, I did not think it was even worth commenting on.

 

[Baylink]

It likely was not: Forward Error Correction is -- by definition -- redundancy. Lack of redundancy is not what causes the Digital Cliff, at least not directly. It can push it back, but you *still* go, jack, from perfect signal to Nothing.

 

[JRayfield]

Simply put, MOTOTRBO will perform at least equal to, and in many cases better than, analog FM. Analog is NOT 'better' than MOTOTRBO in performance. This has been proven time and again with on-the-air systems. And I've seen it myself.

John Rayfield, Jr. - CETma

Baylink, you are right. HiTech twists what I post into something different and then complains that I don't know what I'm talking about. Most of what he accuses me of has no bases in what I posted. I'm done with the discussion as he appears to be someone who just wants to argue.

As for the question of "Which is better", it depends on what you are trying to do. If you are only interested in voice communications then analog is better. But if you want to integrate voice with control and data channels then digital is better. But, like I said, this is my last post on the subject. Bye all!!! Happy New Year!!

 

[Baylink]

I hate to tell you this, John, but you're kinda flag-waving.

Without defining, rather precisely, *exactly* what you mean by "perform better than", this is a fruitless argument, because each party will have a different opinion.

So, in the interest of all that glowy good feeling we're supposed to get from a New Year, I recommend we so define... or drop this thread.

 

[JRayfield]

The comments have suggested that usable audio can be recovered from a weak analog fm signal where digital (and I'm speaking of MOTOTRBO, right now) would 'drop off a cliff', at the same point of signal level, thus resulting in analog being 'better' because it could be 'understood' while the MOTOTRBO digital signal would be 'gone'.

The fact is, when the signal is still 'readable' (even just barely), MOTOTRBO will usually recover that signal and give perfect 100% copy. When the analog signal gets so noisy that it's 'unreadable', then the MOTOTRBO signal will start to become 'twisted' and start dropping audio.

John Rayfield, Jr. - CETma

I hate to tell you this, John, but you're kinda flag-waving.

Without defining, rather precisely, *exactly* what you mean by "perform better than", this is a fruitless argument, because each party will have a different opinion.

So, in the interest of all that glowy good feeling we're supposed to get from a New Year, I recommend we so define... or drop this thread.

 

[Baylink]

The comments have suggested that usable audio can be recovered from a weak analog fm signal where digital (and I'm speaking of MOTOTRBO, right now) would 'drop off a cliff', at the same point of signal level, thus resulting in analog being 'better' because it could be 'understood' while the MOTOTRBO digital signal would be 'gone'.

Correct; that's what we're asserting. I have not personally done tests where carrier strength is measured in uV/m to compare 'equivalent signals', but my understanding is that such tests have in fact been done.

The fact is, when the signal is still 'readable' (even just barely), MOTOTRBO will usually recover that signal and give perfect 100% copy. When the analog signal gets so noisy that it's 'unreadable', then the MOTOTRBO signal will start to become 'twisted' and start dropping audio.

My guess here is that you're comparing "just barely readable" signals for *each separate modulation method*, while not taking into account that those levels, in uV/m, will be different for the two modulation methods; that is, your argument's circular.

You're the CET: can you yourself produce, or conduct, experiment(al result)s which show that *for the same received signal strength*, that when that signal is reduced to the point where even with repeats and such, it's only just barely possible to get audio out of it using 12.5kHz F3E, that DMR still has a clean lock on it? Graphs showing the observed BER in the DMR decoder vs power level would be nice too.

In short: that's an extraordinary claim, based on the current known universe of opinions concerning digital modulation; be prepared to provide extraordinary proof.