Marine band going digital

[mmckenna]

Want to laugh at this?

https://www.nist.gov/document/tr-15-520pdf

You mean this part?

Overall, we conclude that there are multiple audio coding options that can deliver speech intelligibility that meets or exceeds that of the typical analog FM system used in public safety communications, even in the context of multiple diverse and harsh public safety noise environments. And as expected, the success of various audio coding options clearly depends on the data rate available for transmission of the digitally coded audio.​

And like I've said earlier, the standard hasn't been released yet, so passing judgement on a non-existent standard isn't a valid argument.

 

[KC3ECJ]

You are being obtuse.
Read the data again.

 

[mmckenna]

You are being obtuse.
Read the data again.

I did. What was your point in posting that? You obviously think it proves your point, but it doesn't. It makes me think you cherry picked data out of a 7 year old report. If you read the whole thing, it covers it very well. The paragraph I shared was their own conclusion from page 37.

Technology has advanced, and it will continue to advance. When digital cell phones first came out, they sounded terrible. NexTel was nearly unusable. But time and technology marches on and solves those issues.

 

[RFI-EMI-GUY]

Want to laugh at this?

https://www.nist.gov/document/tr-15-520pdf

Table 9 on page 35 tells the tale. P25 intelligibility is inferior to even NB analog FM. I don't know how anyone can debate what users and NIST have said for decades.

 

[RFI-EMI-GUY]

I did. What was your point in posting that? You obviously think it proves your point, but it doesn't. It makes me think you cherry picked data out of a 7 year old report. If you read the whole thing, it covers it very well. The paragraph I shared was their own conclusion from page 37.

Technology has advanced, and it will continue to advance. When digital cell phones first came out, they sounded terrible. NexTel was nearly unusable. But time and technology marches on and solves those issues.

I respectfully submit that you are the one who is cherry picking..

The report concludes that vocoders using greater than 5.9 and 4.4 KBps rate are equivalent or better than analog FM. P25 IMBE/AMBE is not one of those better vocoders. In fact the better vocoders require a wide channel bandwidth to deliver improved performance/

"Finally, we provide some broader conclusions drawn from those very specific statistical tests. In the quiet environment we observe that digital speech coding is very effective from an intelligibility perspective. Table 9 shows that only three codec modes at the very lowest rates (4.4 and 5.9 kb/s) fail to match the intelligibility of AFM."

None of those better vocoders are used in P25 or any other PS LMR application in the US. P25 is pretty sucky per the data presented in the report.

By the way, there have been a couple of studies regarding deficiencies of P25 audio in fire ground communications. The selection of IMBE was really not as rigourous as the application required.

 

[mmckenna]

Table 9 on page 35 tells the tale. P25 intelligibility is inferior to even NB analog FM. I don't know how anyone can debate what users and NIST have said for decades.

P25 did sound pretty bad originally, especially in high noise environments. There's documented cases of fire fighters dying due to communications issues. There were lawsuits. Then the manufacturers got much better at dealing with background noise and solved a lot of the issues. Modern (not 2015) radios have some pretty amazing noise suppression capabilities. Again, it comes down to who programs the radio and is putting the work into setting it up right. Random Joe ham buying an Astro radio off e-Bay and downloading bootleg software off some .ru site isn't going to have the same results.
And considering P25 is a standard that is old enough to vote at this point, it's probably not a good benchmark to use.

While the bandwidth isn't there to do it, digital audio using G.711 sounds pretty damn good. We're using it on our IP phones at work and the difference between POTS and VoIP is like AM broadcast versus FM Stereo.

When I was first looking at replacing the analog trunked system, I trialed some early Motorola Trbo radios. Early models, early firmware, and they sounded like crap. I then trialed some NXDN and was sold.
Since then, technology, firmware and noise suppression has advanced and most MotoTrbo sounds OK at this point.

It's important to acknowledge that the modulation scheme is only part of the equation. Modern noise suppression makes a big difference, and comparing 2010 or 2015 technology to what is available now isn't going to work. Just like when ITU finally settles on a standard in a few years, it'll probably be using technology better than we have now.

Again, the standard is not been released, so drawing conclusions between 10 year old digital radios and what we end up with isn't going to stand the test of time.

 

[mmckenna]

By the way, there have been a couple of studies regarding deficiencies of P25 audio in fire ground communications. The selection of IMBE was really not as rigourous as the application required.

Yeah, see my comment above. IMBE sucked, and so did early P25. APCO stuck with it, but it's 20+ year old technology.
It won't match up with a digital radio we ~might~ get in 2030's.

 

[mmckenna]

The report concludes that vocoders using greater than 5.9 and 4.4 KBps rate are equivalent or better than analog FM.

While the standard has not been set, there was discussion of similarities between dPMR and the proposed 6.25KHz digital that was being suggested for marine VHF.
If you look at 6.25KHz NXDN, you can get ~about~ 4.8k out of it. 12.5KHz NXDN will give you about 9.6K.

Who knows what ITU will pick. Just because they are looking at 6.25 4 level FSK now doesn't mean that's what they'll settle on. Maybe they'll use a higher level FSK and squeeze a higher data rate out of it.

Having used P25 and NXDN side by side, NXDN sounds better, and it's less expensive when implemented.

 

[RFI-EMI-GUY]

P25 did sound pretty bad originally, especially in high noise environments. There's documented cases of fire fighters dying due to communications issues. There were lawsuits. Then the manufacturers got much better at dealing with background noise and solved a lot of the issues. Modern (not 2015) radios have some pretty amazing noise suppression capabilities. Again, it comes down to who programs the radio and is putting the work into setting it up right. Random Joe ham buying an Astro radio off e-Bay and downloading bootleg software off some .ru site isn't going to have the same results.
And considering P25 is a standard that is old enough to vote at this point, it's probably not a good benchmark to use.

While the bandwidth isn't there to do it, digital audio using G.711 sounds pretty damn good. We're using it on our IP phones at work and the difference between POTS and VoIP is like AM broadcast versus FM Stereo.

When I was first looking at replacing the analog trunked system, I trialed some early Motorola Trbo radios. Early models, early firmware, and they sounded like crap. I then trialed some NXDN and was sold.
Since then, technology, firmware and noise suppression has advanced and most MotoTrbo sounds OK at this point.

It's important to acknowledge that the modulation scheme is only part of the equation. Modern noise suppression makes a big difference, and comparing 2010 or 2015 technology to what is available now isn't going to work. Just like when ITU finally settles on a standard in a few years, it'll probably be using technology better than we have now.

Again, the standard is not been released, so drawing conclusions between 10 year old digital radios and what we end up with isn't going to stand the test of time.

As you say, the bandwidth isn't there to make even G.711 work.

Narrow band in some areas of Europe and Asia is 6.25 KHz so should that be an ITU decision, the challenge will be even greater.

Vocoders are very finicky non linear devices. Complex waveforms confuse them and create IM like audio products. Dynamic range is limited compared to analog, thus the audio levels must be tightly controlled and even Motorola does not know where to set default gain and AGC values for even a standard public safety customer let alone their many different products work differently.

You scoffed when I said it will be a $1200 radio. It will be.

 

[RFI-EMI-GUY]

Yeah, see my comment above. IMBE sucked, and so did early P25. APCO stuck with it, but it's 20+ year old technology.
It won't match up with a digital radio we ~might~ get in 2030's.

It all comes back to: why bother? When music CD's came out there was pushback from the analog crowd. But truthfully, music on vinyl is imperceptibly better than a CD to most peoples ears, until the vinyl wears out. How did they get away with it for CD's? Plenty of bits and headroom. The data travels 4 inches over light and wires.

Narrow band radio cannot provide an environment for a vocoder to behave better than analog FM. It could not when APCO wrote the standard, it cannot now. Again why bother? If you want signalling like AIS, dedicate a channel and a modulation for it in the radio.

 

[mmckenna]

Remember, they are not talking about using P25, so using that as the benchmark isn't going to jive with where this is going.
6.25KHz using 4PSK is going to be limited to 4.8K. But there's no standard set yet. They may choose something else after testing is complete. This isn't scheduled to go live until later this decade at the earliest… Again, no standards have been set. Be patient. You are passing judgement on something that hasn't happened yet.

And I wouldn't trust Motorola with this. Just about every major radio manufacturer has done a better job with their digital audio than they have.

As for the cost of radios, we'll have to wait and see. Maybe you are right. But I can buy a NXDN radio right now that will do analog/mixed mode, has Part 80 certification, GPS, IP67 and all the noise suppression options for less than $400.

 

[mmckenna]

Narrow band radio cannot provide an environment for a vocoder to behave better than analog FM. It could not when APCO wrote the standard, it cannot now. Again why bother? If you want signalling like AIS, dedicate a channel and a modulation for it in the radio.

It depends on how they modulate the signal. P25 is pretty old, using older technology. I wouldn't use it as a benchmark for technology that may be coming in 8-10 years.

 

[INDY72]

It depends on how they modulate the signal. P25 is pretty old, using older technology. I wouldn't use it as a benchmark for technology that may be coming in 8-10 years.

Your flogging a dead horse to shreds and wasting your time trying to make a point that the person that is against it is not even capable of wanting to make the slightest effort to comprehend at even the most basic of levels. Its a case of trying to teach a fossilized dog a simple trick. As to those comments about apple fanboy malarkey.. I will never ever use an iSnob product as its overhyped bullshite that is costing 3 times what its worth and is doing the same things the other products not made by 9 y/o slave laborer in ChiCommie sweatshops. When folks were yammering over the old iPods, that were costing $200.00 I had a $50.00 mp3 player doing all the same with the same abilities. Same for your crapped out iPhones. Same for the age old BS war between Apple/Mac vs IBM clones. And as for sound quality and Motorola's... Back in the day I had an HT1250LS+, sounded decent, Then I went to an XTS3000 M3, sounded soooo much better, but nothing compared to my APX6000XE! The quality has improved so much with not only the radios, but the systems they work on! If I ever hit the lotto and could play with a APX NEXT, I bet it would sound even better. As for DMR, I have had the opportunity to use an XPR, and it sounds just as good as my APX. Technology constantly gets better. And NOT always more expensive! Hell my lil CCR sounds decent on DMR, compared to a lot of analog it gets used on.

 

[nsrailfan6130]

I learned something new here. So basically what you are saying if I understood this right (I am still new to baud rates etc) is the higher the data rate the better the sound quality?

While the standard has not been set, there was discussion of similarities between dPMR and the proposed 6.25KHz digital that was being suggested for marine VHF.
If you look at 6.25KHz NXDN, you can get ~about~ 4.8k out of it. 12.5KHz NXDN will give you about 9.6K.

Who knows what ITU will pick. Just because they are looking at 6.25 4 level FSK now doesn't mean that's what they'll settle on. Maybe they'll use a higher level FSK and squeeze a higher data rate out of it.

Having used P25 and NXDN side by side, NXDN sounds better, and it's less expensive when implemented.

 

[mmckenna]

I learned something new here. So basically what you are saying if I understood this right (I am still new to baud rates etc) is the higher the data rate the better the sound quality?

Yes, generally speaking. It has a lot to do with which CODEC is used. Some are better than others.
Kind of the point I've been trying to get across. It's not "analog = good, digital = bad". There's too many variables to make sweeping statements like that. Digital can sound really good, if done right.

 

[nsrailfan6130]

I agree, In Michigan, we pretty much run all kinds of digital except in those areas that run Ana. as a listener, I am embracing digital more because I took the time to at least get an idea as to what it has to offfer. Ana has its place sure, but, it's slowly being replaced by NXDN, DMR, P25 in different arenas Do I like it? Well, at first, I didn't, but only because I didn't take the time to look into it. You used the term codec, how does that work? Is that a proprietary thing?

Yes, generally speaking. It has a lot to do with which CODEC is used. Some are better than others.
Kind of the point I've been trying to get across. It's not "analog = good, digital = bad". There's too many variables to make sweeping statements like that. Digital can sound really good, if done right.

 

[cpetraglia]

Well you don't know what you are talking about and/or are dishonest.

Would you send music over an IMBE or AMBE codec?

You really think that sounds better than even AM broadcast?

These codecs clamp down on sounds they think are interference, but aren't.

I don't think people like you have a clue about bandwidths and the limits those bandwidths put on how much data can be passed.

I know what I've experienced. I also know I am no expert on digital comms, but my ears work fine.

No marine radio system or LE system was designed to carry music. It was specifically designed for data and/or voice. Your argument here is beginning to get obnoxious. Calling people dishonest when you know nothing about them is a non-starter.

 

[vagrant]

@milf If you get the opportunity, try DMR using a Kenwood NX-5300 radio, or at least listen to one. I like it over the XPR and any amateur grade radios. DMR sounds very good from the 5300. Actually, everything sounded good from that handheld.

 

[12dbsinad]

So let me get this straight, when marine band goes digital and you get that "rushing water sound", you won't be able to tell the difference between it being the radio, or the boat sinking?

What good is that?!?

 

[MUTNAV]

So let me get this straight, when marine band goes digital and you get that "rushing water sound", you won't be able to tell the difference between it being the radio, or the boat sinking?

What good is that?!?

If the entire marine band is playing, you could probably here the tubas well enough due to the lower frequencies (and they are a composite analog / digital ), it could be like the titanic with the orchestra playing as it went down.

On the other hand, since this is a serious subject, maybe I should leave it to the pros, with appropriate inputs from the interested parties.

I get it, some people think the audio quality isn't good enough, others do. A boat going down with a digital radio set might be better off with a final digital transmission with its co-ordinates and ID embedded in the transmission, and everyone being able to receive it, on the other hand that could be done with an analog transmission with digital encoding.

I'm sure the ITU will figure it out.

Thanks
Joel