Simulcast Issues - Hardware or Software?

[marksmith]

Can't argue those points.

Generally those using service radios have a reason to be affiliated to the system, and nobody has a reason to receive encrypted transmissions other than those involved with those systems.

536/436/ws1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others

 

[RF-Guy-El-Loco]

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.

 

[BenScan]

I find the Unication G4 and G5 radios to be an affordable solution to monitoring LSM systems. Yes, they cost a little more than cheaply designed and manufactured scanners, and they're more challenging to program, but they actually WORK! If you figure in the cost of your time, antennas, and cables that you waste on cheap scanners, the cost difference is even less. I don't know if I'll ever buy another scanner, until they fix LSM reception. I honestly don't think Uniden and Whistler are listening or care to provide the product that so many of us want. What's really sad and aggravating is they have LSM systems in their own backyards here in the Dallas/Fort Worth area and haven't done anything about it.

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.

 

[Jimco]

What's really sad and aggravating is they have LSM systems in their own backyards here in the Dallas/Fort Worth area and haven't done anything about it.

This is my main aggravation as well. My primary beef is that Uniden KNOWS that their scanners stink on these systems, but they still market them to people who want to monitor these systems. That's why so many people end up struggling to use paper clips, custom antennae, and more to try and work around these limitations. Ultimately, these solutions also stink and folks end up with a $400 paper weight. It's really shameful.

Jim

 

[eorange]

Uniden can't fix things given the existing hardware, otherwise they would have already. Any other solution requires better hardware which would price them out of the consumer market.

And that's the problem...looking for a professional solution from a consumer company.

Sent from my SAMSUNG-SM-J320A using Tapatalk

 

[CanesFan95]

I think there is a market though. Scannists are snatching up Unications at $700 a pop, and Uniden Functionality blows away Unication for scanning. So if you take the Unication guts and add Uniden scanning features and slap it all together in one box, it'll be a slam-dunk, even at $1,000 - $1,200. I betchya.

 

[jcardani]

If everyone searches for Max Parks's (KA1RBI) many posts on this topic he explains the issue with consumer scanners very clearly. It is a hardware issue. Also see his web pages:


LSM 101

LSM Gallery - Page 2

A 455 KHz IF Downconverter for Digital Radio Reception

https://forums.radioreference.com/v.../283705-lsm-why-scanners-suck-real-story.html

So the answer to the question is that you don't need expensive hardware to properly decode LSM. A hardware re-design (I-Q based demodulator vs. limiter-discriminator) coupled with modified firmware (such as a Costas Loop/Gardner Clock recovery method) would be required to be implemented in the consumer scanners.

 

[eorange]

I think there is a market though. Scannists are snatching up Unications at $700 a pop, and Uniden Functionality blows away Unication for scanning. So if you take the Unication guts and add Uniden scanning features and slap it all together in one box, it'll be a slam-dunk, even at $1,000 - $1,200. I betchya.

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.

Sent from my SAMSUNG-SM-J320A using Tapatalk

 

[RFI-EMI-GUY]

OK it's late, I am not thinking clearly, but I will try. I have this idea, an add on board that properly decodes LSM in hardware, then turns around and presents the recovered data as C4FM.

One would take this board, cut the IF signal just before the discriminator in a Uniden or Whistler, reinsert the reprocessed IF and C4FM to the scanner discriminator.

Sent from my SM-T350 using Tapatalk

 

[slicerwizard]

This idea has been proposed before and it's certainly doable. Not easy, but doable.

 

[jcardani]

I had the same idea several years ago. Thought about using a CML Micro chip for that purpose.

Andrew is right, it would be a difficult task.

Joe

OK it's late, I am not thinking clearly, but I will try. I have this idea, an add on board that properly decodes LSM in hardware, then turns around and presents the recovered data as C4FM.

One would take this board, cut the IF signal just before the discriminator in a Uniden or Whistler, reinsert the reprocessed IF and C4FM to the scanner discriminator.

Sent from my SM-T350 using Tapatalk

 

[KA1RBI]

It would be difficult, and IMHO not worth the trouble, but it's still interesting to speculate about.

cut the IF signal just before the discriminator

I don't have the current Uniden and Whistler schematics and/or block diagrams, which adds to the level of conjecture here ... but in all these previous-generation circuits if you cut the IF prior to the discriminator it also breaks the AGC loop. Fixing that is one of the Unanswered Questions. It *could* be that a better point to cut would be after the output of the discriminator at the baseband input to the DSP chip...

73

Max

 

[CanesFan95]

So if we don't need expensive hardware, then why the hell won't Uniden do it already?

 

[RFI-EMI-GUY]

It would be difficult, and IMHO not worth the trouble, but it's still interesting to speculate about.



I don't have the current Uniden and Whistler schematics and/or block diagrams, which adds to the level of conjecture here ... but in all these previous-generation circuits if you cut the IF prior to the discriminator it also breaks the AGC loop. Fixing that is one of the Unanswered Questions. It *could* be that a better point to cut would be after the output of the discriminator at the baseband input to the DSP chip...

73

Max

If you grab the demodulated signal at the discriminator, you have no amplitude component to work with, you still have the same problem.

Not sure how the AGC loop is configured in all these receivers, most commercial FM radios go into hard limiting before the discriminator, so the loop might have to pick it up there. Is there even AGC in the FM mode? maybe in AM mode averaged from the AM detector? Now I have to look at schematics.

My point is, that a drop in board solution might be possible, maybe not something Whistler and Uniden would sanction. But there would be a market for it. Especially if it could retrofit back a couple generations of trunk scanners.

Back in the heyday of shortwave radios, Sherwood made a killing with synchronous AM detectors, custom IF filters and the such that found there way into high end SW radio equipment.

If it could work, I would buy one. It would be cheaper and less hassle than a non affiliated scan programmed Motorola radio. I don't think a non affiliated scan mod will work with phase 2 so there is that.

 

[RFI-EMI-GUY]

So if we don't need expensive hardware, then why the hell won't Uniden do it already?

Because, some software guy figured he could make it work from a discriminator and the design got locked in that way. It works great enough for maybe 85% of the users, is tolerable for another 15% (me) and the rest figure they were just not smart enough to program the radio so it either gets put on a shelf or returned.

Until Uniden recovers their investment in the X36 product line, they won't bother to fix the problem. If they did, then everyone would want an upgrade (like the radio shack/whistler fiasco).

If some smart guy makes a drop in board that fixes it without messing with the copyrighted firmware he would have gold. He could sell retrofit boards, sell radios with his mod, or accept radios for up-fitting.

 

[CanesFan95]

And just who is this "software guy"?

 

[KA1RBI]

If you grab the demodulated signal at the discriminator, you have no amplitude component to work with, you still have the same problem.

Quite right - I'm saying you would cut the trace between the discriminator output and the DSP chip in the scanner, and connect the output of the "new add-on board" to the input pin of the DSP chip. This connection would be at AF and is conceptually sort of like a Virtual Audio Cable

The add-on board would get its input signal via a tap of one of the IFs, presumably the final IF - but there would be no cut at that point in the scanner, which preserves the AGC circuit (with a caveat that the scanner's AGC response isn't necessarily optimal for that type of signal)...

73

Max

 

[CanesFan95]

No clue what you guys are talking about or where on earth to learn all this. But I'm sorry, Uniden needs to hire you all. NOW.

 

[RFI-EMI-GUY]

And just who is this "software guy"?

Some poor kid, learning on the job. His manager said, "we will fix it in software" no problem!

 

[jcardani]

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)