Simulcast Issues - Hardware or Software?

[RFI-EMI-GUY]

I was originally thinking about this chip for the task:

Digital-radio Baseband Processor - CML Microcircuits

which can be used for non-Tetra radio schemes using Pi/4DQPSK (like P-25 simulcast)

I am not familiar with this chip. The C4FM and GMSK modem chips, I have studied.

I see CML has posted an end of life notice, in their words "not recommended for new designs". It looks like the I/Q modem functions are outboard? Could this same chip be operated duplex and be programmed to simultaneously generate a corresponding C4FM output to drive the discriminator while filtering the P25 LSM waveform? Or would two chips be required, this chip and a C4FM modem.

 

[KA1RBI]

programmed to simultaneously generate a corresponding C4FM output to drive the discriminator while filtering the P25 LSM waveform?

I confess to not being very familiar with FMP - but I thought that's basically what it does when running in CQPSK mode? Doesn't it regenerate and output a "fake" C4FM signal using VAC to drive the remainder of the legacy stack? Or something like that? If so then the entire thing already exists as a building block?

Max

 

[carnch]

I know there is a huge difference between our consumer grade scanners and the Pro Grade service radios. I'm lucky that my residence ended up being in a good RF signal location for APCO P-25 digital, it works like it should with the scanners I own at my residence. I'm not in need of DMR yet. And I don't have LSM simulcast distortion. But we are all basically asking a whole lot from a consumer hobby radio sold to make a profit off of an advanced (but diminishing) chunk of hobbyists in the general public. I went broke buying the scanners I do have. The scanner reception is flawed because it is cost prohibitive to make it a service grade radio perfect for every thing that we want it to do, DMR, P-25, analog too, etc. We only have two manufacturers making these things now, remember this, and I don't see the market growing any. The engineers aren't sitting around laughing at us. It would probably take a much more advanced or expensive New CPU (hardware) to get any better LSM performance out of it now. If they truly could fix it in software decode they would've already done it as they read every word we post about these issues. They can't make it work 100% perfect for every possible scenario at every possible location.

There may not really be a cheap fix to LSM simulcast distortion without moving. I worked for an FM station in Chicago where our target audience (the big donors) lived mainly on the North side and had severe multipath distortion issues due to signal reflections from the tall buildings. For some, they simply couldn't listen to the station at all, no matter what radio/antenna they used. The only real fix we had was to tell them that they were in a "bad reception shadow area" and outside of moving, there wasn't much we could do. Then we started a high quality web stream and they could hear finally hear us again.

Although I agree that the scanner manufacturers can't make their products work 100% perfect for every possible scenario I refuse to believe that fixing the LSM issue would be too costly, at least in new scanners, even if they can't come up with a software fix for current hardware. If a $20 DVB dongle and a piece of well-written software is able to properly decode a P25 type I/II system with little to no distortion in the audio that tells me that with a cheap hardware change and a software redeign the scanners could be made to work well on a simulcast system. It doesn't need to be professional grade audio, it just needs to work.

I also disagree that we (the hobbyist) are asking too much from the scanner manufacturers. Look at analog trunking systems. When they first arrived on the scene the scanner makers could have ignored this as it was still possible to listen to the trunked systems by scanning the conventional frequencies, but then most people would have been in the same boat we are in now which is looking for a commercial grade radio so they could properly "follow" a conversation. Instead, scanner makers chose to upgrade the technology in the scanners to support trunking and raise the prices, and we bought them. When digital systems first became popular the manufacturers created digital scanners at twice the cost and we still buy them. I don't see why fixing the LSM issue would be any less of a priority. In fact, as more and more public safety systems move to P25/simulcast technology the current scanners will become less useful. Sure, there are other things we can listen to but lets face it, a majority of the scanner hobbyists listen to first responders and less are able to do so because of this issue. Why do you think there are so many people moving to commercial grade radios?

The only reason I can think of for scanner manufacturers to ignore this issue is because, like RF Guy said, they think it is a dying hobby but anyone reading these forums (and others) can see that this is not the case. People are simply abandoning scanners for other means of listening because of the limitations. In a way, by ignoring this issue, the scanner manufacturers are causing their own demise by not fixing something as problematic as the LSM distortion issue.

Just my two-cents

 

[RFI-EMI-GUY]

Although I agree that the scanner manufacturers can't make their products work 100% perfect for every possible scenario I refuse to believe that fixing the LSM issue would be too costly, at least in new scanners, even if they can't come up with a software fix for current hardware. If a $20 DVB dongle and a piece of well-written software is able to properly decode a P25 type I/II system with little to no distortion in the audio that tells me that with a cheap hardware change and a software redeign the scanners could be made to work well on a simulcast system. It doesn't need to be professional grade audio, it just needs to work.

I also disagree that we (the hobbyist) are asking too much from the scanner manufacturers. Look at analog trunking systems. When they first arrived on the scene the scanner makers could have ignored this as it was still possible to listen to the trunked systems by scanning the conventional frequencies, but then most people would have been in the same boat we are in now which is looking for a commercial grade radio so they could properly "follow" a conversation. Instead, scanner makers chose to upgrade the technology in the scanners to support trunking and raise the prices, and we bought them. When digital systems first became popular the manufacturers created digital scanners at twice the cost and we still buy them. I don't see why fixing the LSM issue would be any less of a priority. In fact, as more and more public safety systems move to P25/simulcast technology the current scanners will become less useful. Sure, there are other things we can listen to but lets face it, a majority of the scanner hobbyists listen to first responders and less are able to do so because of this issue. Why do you think there are so many people moving to commercial grade radios?

The only reason I can think of for scanner manufacturers to ignore this issue is because, like RF Guy said, they think it is a dying hobby but anyone reading these forums (and others) can see that this is not the case. People are simply abandoning scanners for other means of listening because of the limitations. In a way, by ignoring this issue, the scanner manufacturers are causing their own demise by not fixing something as problematic as the LSM distortion issue.

Just my two-cents

I was more than a bit disappointed to learn after the fact that the 536HP suffered LSM after reading a bunch of hype that it had improved simulcast performance. It is a great receiver in a lot of ways, but I know I am missing a lot of traffic and there are gaps and unexplained constant DAT/LNK icon blinking while idle.

Prior to buying the 536HP, I was using a Spectra mobile programmed properly to listen the local analog simulcast system (I had the CC skillz) before the digital transition. Now with digital and issues with auto-affiliation (danger will robinson) and ASK, I thought the 536HP was the answer.

 

[RF-Guy-El-Loco]

The Great Oracle, Drunkard will now see us into the future. "I see a strange man bent over at a bench with a bunch of small wires and parts. I see a computer running Python under Linux. I see heat and smoke rising from a tiny perf board with a bunch of micro SMD components on it. I see wires coming from this small gadjet going into a receiver of some kind. I see the man working on many of these little things. I see a "Cease and Desist" letter coming in the mail from a large Japanese company."

 

[CanesFan95]

I paid nowhere near $700 for my Unication. And all that 'functionality' don't mean squat if all you're hearing are broken transmissions.

The only way I'd pay more than 1G for a radio is if it had transmit, or coverage of a couple GHz.

Regardless...perfect, distortion free P25 reception can be had right now for about $70 more than a BCD436HP.

Not if you need Phase 2. And Ray's pagers has the G5 for about $660. That is near $700.

 

[Jimco]

I was more than a bit disappointed to learn after the fact that the 536HP suffered LSM after reading a bunch of hype that it had improved simulcast performance. It is a great receiver in a lot of ways, but I know I am missing a lot of traffic and there are gaps and unexplained constant DAT/LNK icon blinking while idle.

This is exactly why I originally asked the question. I didn't know about these LSM issues until after I had purchased my 436. Even after I realized it had LSM issues, I still had days when it sounded very good and I thought I was hearing everything, but now that I have a G5 and I've run side-by-side tests, I realize that, even on a good day, my 436 is completely missing many transmissions.

I don't agree that hobbyists are not willing to pay for the hardware, and I reject the premise that the problem is that I am expecting professional results from a consumer product. In the case of the former, I paid $800 for a G5 and the amplified charger, and that was less than a year after dropping about $500 on the 436. (Many others are doing the same thing.) As for the latter, one should expect intelligible reception from any receiver that is designed to listen to P25 systems, and if Uniden can't deliver on that, they should make sure that consumers know in advance that it may not work.

Jim

 

[KA1RBI]

... I reject the premise that the problem is that I am expecting professional results from a consumer product ... one should expect intelligible reception from any receiver that is designed to listen to P25 systems, and if Uniden can't deliver on that, they should make sure that consumers know in advance that it may not work.

Very well said. I would go even further - with respect to Phase II/TDMA, I'd argue these scanners are not even compliant with the P25 specification....

73

Max

 

[eorange]

and I reject the premise that the problem is that I am expecting professional results from a consumer product...and if Uniden can't deliver on that, they should make sure that consumers know in advance that it may not work.

Uniden is in the business to sell scanners. Would anyone really think they'd footnote their flagship product with:

* may result in broken transmissions
* may miss transmissions completely
* may not perform as expected in simulcast regions

But, they don't have to. That's what this place is for.

 

[Jimco]

Uniden is in the business to sell scanners. Would anyone really think they'd footnote their flagship product with:

* may result in broken transmissions
* may miss transmissions completely
* may not perform as expected in simulcast regions

But, they don't have to. That's what this place is for.

I think there are a lot of hobbyists who don't know to search these forums before making a purchase. Honestly, I think if Uniden is really interested in selling scanners, it would be in their best interest to do just what you propose! By not doing that, what they've done is breed ill-will towards them from all of those who feel as though they've been suckered, myself included.

Jim

 

[eorange]

I think there are a lot of hobbyists who don't know to search these forums before making a purchase. Honestly, I think if Uniden is really interested in selling scanners, it would be in their best interest to do just what you propose! By not doing that, what they've done is breed ill-will towards them from all of those who feel as though they've been suckered, myself included.

Jim

Believe me, I totally get what you're saying. But almost no company will risk jeopardizing their bottom line by being 100% truthful.

Sent from my SAMSUNG-SM-J320A using Tapatalk

 

[Jimco]

Believe me, I totally get what you're saying. But almost no company will risk jeopardizing their bottom line by being 100% truthful.

That's probably so, but I hope that possibly Uniden will hear from this thread that it might be a good approach. Personally, I would have a lot more admiration and respect for them if they had been truthful and saved me a few hundred bucks!

Jim