Audio Quality: Dstar vs. P25 vs. DMR

[N8OHU]

DStar absolutely fits in a 6.25Khz channel. That's a FACT. Not sure where you got your belief that it does not, but you are not correctly informed.

Well, the older radios didn't; the Utah VHF Society tests he's referring to show that for the two radios they tested (Icom IC2200H and Icom IC-91A(D) ) the RF bandwidth for the GMSK modulated signals was between 7k and 9k

Some earlier DStar radios possibly could not tune in 6.25 increments, but they could be memory programmed to store the newer channels. I have four DStar radios and have not found a repeater that could not be programmed into memory.

As for testing. Really who cares. You have to be the first individual in three years (since I have been using DStar who brought up that issue. It apparently is not an issue with the vast majority of hams.

Only those that believe that a viable digital voice mode MUST have detailed diagnostic documentation published; since D-Star was designed first and foremost to encourage experimentation with digital voice and data technology, there is less of a need for that.

DStar is THE standard for amateur digital radio at this point whether you like it or not. Everything else is a distanced minority. That is a FACT as you like to point out. Sure you can play for P25, DMR, and all the other commercial stuff that does not work as well in the amateur radio market, but it still is a commercial standard with commercial technology for a commercial market. Amateur radio does not have talk groups, radio IDs. We have call signs and multiple radios.

Agreed; DMR (at least MotoTRBO) is too dependent on "approved" hardware and software to work well as an Amateur Radio system, though I think Mr. Rayfield might not like hearing that. The truth is, the more complex you make a system, the less it works as intended; it might seem to work well at first, but the nature of TDMA is actually working against those that use it in ham radio, at least as currently deployed.

So if you actually want to talk to someone, get a DStar capable radio. Tens of thousands of users. Close to 2,000 repeaters worldwide. Get some other digital commercial radio, and you'll hear the sound of crickets, but only if standing outside.

Yes, and you get a lot of choices in nets on D-Star; I believe there are nets on the various reflectors nearly every night of the week, whereas there are only two that I know of on the MotoTRBO World Wide system. Plus, some reflectors (mostly DExtra and DCS) have bridges to analog FM, Echolink and IRLP (I know this can be done on local talkgroups on DMR), but these are full time available to all users that connect to the reflector.

 

[beischel]

But that assumes they performed the testing correctly.

I am very suspect of anyone saying the transmitted signal is wider than 6.25Khz. Given the filters on the receivers of the repeaters and other DStar radios and the fact that the first DStar radio has no problem working with the current 4th generation set of radios, I am not sure their testing is accurate.

 

[WA9TED]

That is the other thing I never liked about D-Star when someone tries to speak it's like all robot voice when someone isn't close to the system and etc I wish they would fix this problem or they might have a fix for it.

I would disagree, I operate portable from at least 18 miles from my repeater and I live at the bottom of a valley. I can do this on both 2 meters and 440. I agree that the audio quality isn't the best, but I don't think P25 is all that better, maybe more bass. Statistics prove that digital as opposed to analog gives about 30 percent more distance in signal.

 

[JRayfield]

Just thought I would comment on the differences in audio quality of the different digital formats.

First of all, differences in audio quality can vary, based on who's hearing the audio. In other words, "audio quality is in the ears of the listener".

Many years ago, I had a customer on my UHF LTR trunked system, who kept complaining that he had trouble understanding the audio on the Motorola radio in his truck. We checked the radio several times and never found anything wrong. The audio sounded great. Then, one day when he was back in the shop, again complaining of not being able to understand others when they called him on the radio, he happened to mention that he as almost deaf in one ear. So we mounted an external speaker just off to the side of his head, on his 'good ear' side. That completely solved the problem.

Hearing problems can be related to frequency response, too. So, one person may listen to a radio and hear 'good quality audio', while another person may listen to the exact same radio and hear 'poor quality audio', the difference being caused by a different frequency response in their hearing.

So, in comparing the audio quality of digital communications systems, it can become difficult to get a report of "good quality audio" from all users of a particular system.

With all of the above said, here are my experiences. I've been using MOTOTRBO (XPR series radios) since shortly after MOTOTRBO was introduced to the market. I also just purchased one of ICOM's new ID-51 D-Star portables at Dayton. And, just a few days ago, I had the opportunity to hear the audio on a Hytera DMR mobile (very new, so likely fairly new firmware, if not the newest).

In comparing MOTOTRBO (the XPR series of radios, both older series and new series) to the ID-51 D-Star radio, I would say that the audio quality is very similar. Both sound quite 'natural', especially for a digital protocol. Any differences between the two might likely be due to differences in frequency response of the listener's hearing (as I mentioned above).

In comparing MOTOTRBO XPR series radios to the Hytera mobile, the Hytera radio sounded much more 'robotic'. Interestingly, I would say that the Hytera radio sounded more like MOTOTRBO radios sounded, early on with early firmware. Motorola engineers have been able to improve the audio quality of the XPR series radios, considerably, with several new releases of the firmware for these radios. Yes, the firmware in the radio can have a great bearing on the audio quality of the radio - it's not just the vocoder itself that has such a bearing, but the firmware that operates with the vocoder, too.

So, it would appear to me that ICOM and Motorola are both 'well ahead' of Hytera, in terms of the engineering behind the 'audio quality' of their respective digital formats.

Of course, again, others may not agree with my conclusions here, but that is really to be expected, since different people hear things 'differently'.

John Rayfield, Jr. CETma
W0PM

 

[brushfire21]

John, what about the audio differences between the D-star and DMR as far as how they handle being at the edge of reception and audio quality?

 

[AA9VI]

Here's an important point:
throw out many of those YouTube videos of comparisons. Why?
Do the TRBO radios use
- Firmware newer than R01.08.00
- AGC disabled

These are very important factors. With these two set properly MOTOTRBO DMR is much better than D-star. These are the settings promoted by DMR-MARC, a network of over 180 DMR repeaters worldwide. When TRBO radios are set this way they seem less discretely sampled and have much better low frequency emphasis. (D-star tinny sounding due to much more high frequency emphasis on the audio) If you do not set these two right I think the D-star audio is slightly better.

so, go ahead and make those changes then rebenchmark. We'd all be interested in the tests then. Until then, comparisons with an old radio are not accurate.