Uniden P25 Simlucast - Possible Solution to Ponder

[mancow]

With no schematics available how would an add on board ever be developed without some extensive reverse engineering?

 

[slicerwizard]

It shouldn't be that hard to probe the RF board for the IF signal of interest. Not sure that it's a practical idea though. If the intent is to have a high performance radio, buy a real (Motorola) radio. If saving money is the goal, use a DVB-T dongle or two and do it all in software.

 

[JamesO]

So Unidens have reference clocks that are so jittery and/or off-frequency that they can't handle slow 4800 or 6000 baud symbol streams? And fixing the clock will yield a 50% improvement? This is what you're suggesting? Are you aware that software decoders (TRUNK88, UT, DSD+, ...) don't even have reference clocks? No offense, but you're sounding as far off base as the thread starter.

I never stated that the Uniden referece was so jittery and off-frequency. I also did not state there would be a 50% improvement.

I was hypothesizing that MAYBE if a more stable base reference was used then MAYBE there could be an improvement. Not a 100% improvement, but MAYBE some improvement. Maybe a 50% improvement?? Would people be happy with a 50% improvement?? Seems that everyone today is so digital, they will settle for nothing short of perfection, otherwise live with what you were handed.

I look at the world that sometimes an incremental improvement or a small percentage improvement may be worth the effort, but until you can make the change and test it, NOBODY has any idea as to how things would be with a partial improvement.

Kind of funny how you state that software decoders have no base clock, maybe they don't but I would bet that the software decoders use the computers time base as a trigger.

Almost ANY RF or data circuit had some form of reference clock, not sure how the world would work without one.

You say I am far off base, do not think so.

Again, there is a LOT of talk about how experimenting and trying certain out of the box ideas will not work, BUT until the experimentation and out of the box ideas are tested NOBODY knows the answer.

I am short on time at the moment, but when I get a chance I will investigate the base clock and maybe try a more stable reference JUST to see what happens. Maybe NOTHING, maybe an improvement, let the data speak for itself.

Until someone tries, we will never know!!!

I can screw up more things in 5 minutes playing with equipment or software that takes most Beta testers months to even find part of the issues I find.

I dive in head first with no bias about how something should be programmed or configured and if they there is menu or a button I am tying all options. Kind of funny how in as little as 5 minutes I may have painted myself in the corner using the tools, settings and options that are provided and then when I flag something, the software/firmware/developers look at me and say "your not supposed to do that"!!!

Well if the configuration, menus or software options allow me to paint myself into the corner, then there is a problem with the configuration, menus or software!!! Something is not right and there are not enough checks and balances.

When I have time, I WILL be playing with the base clock, using a more stable time base reference as well as seeing what else I can find good, bad or indifferent.

Specs are specs, real world measurements and test mean a lot more. I have found more problems with bad hardware that does not meet spec, bad firmware that does not function properly in my days that I can even care to keep track of. It is always amazing how some vendors claim all day they have no issues, then I uncover something, and I toss if back to the vendor and tell them to figure out why something does not meet spec or does not work as advertised. I have even caused worldwide shut down on products that a vendor swore was fine and the problem I uncovered had been around for about 2 years, so when I started to question things the vendor kept blowing me off as they were like this product had not changed in 2 years, well guess who was wrong and had to eat a crow on that issue.

 

[slicerwizard]

I never stated that the Uniden referece was so jittery and off-frequency.

Then where would your maybe 50%?? improvement come from? Sounds like you're trying to move the goalposts.

Kind of funny how you state that software decoders have no base clock, maybe they don't but I would bet that the software decoders use the computers time base as a trigger.

These days, we record audio files, upload and download them, then feed them to DSD+; why would DSD+ think "Hm, I'd better check the PC's time base every now and then as I munch through this audio data... Wait a sec, what am I checking for?"

Almost ANY RF or data circuit had some form of reference clock, not sure how the world would work without one.

Well, I can post links to some raw audio files that DSD+ will decode perfectly. The only clock involved is the sound hardware's sampling clock, and those are anything but precise. LTR Analyzer, for example, uses 22 kHz sampling (22050 Hz), but due to driver bugs, sound hardware might actually serve up 22222 Hz or 21600 Hz audio (a whopping 2% error), but LTR Analyzer just plods on, serving up clean decodes. TRUNK88 does the same thing with 3600 bps data - 21600 Hz sampled audio decodes just as well as 22050. So a super-accurate clock isn't a requirement.

I am short on time at the moment, but when I get a chance I will investigate the base clock and maybe try a more stable reference JUST to see what happens. Maybe NOTHING, maybe an improvement, let the data speak for itself.

You'll be generating data? You'll have a repeatable RF input to the radio for your A/B testing and you'll be extracting BER measurements from the radio via a serial or USB connection? Or will you just be using your Mark I ear? Can it hear a 5-10% improvement? (I doubt it...)

I dive in head first with no bias about how something should be programmed or configured and if they there is menu or a button I am tying all options. Kind of funny how in as little as 5 minutes I may have painted myself in the corner using the tools, settings and options that are provided and then when I flag something, the software/firmware/developers look at me and say "your not supposed to do that"!!!

Well if the configuration, menus or software options allow me to paint myself into the corner, then there is a problem with the configuration, menus or software!!! Something is not right and there are not enough checks and balances.

You'd be well on your way to a 50% improvement if you discovered that Uniden didn't implement Golay FEC on IMBE voice frame data, but alas, they already do. But your clockwork won't find any firmware bugs, even if those that may exist.

When I have time, I WILL be playing with the base clock, using a more stable time base reference as well as seeing what else I can find good, bad or indifferent.

Fine by me. It's your time to do with as you see fit. Seriously, there is nothing wrong with experimentation, so go for it, but let's keep our expectations realistic...

 

[Alliance01TX]

Ponder vs The Impossible....

General Point - Only directed to those that "if the shoe-fits"....

James makes valid pointts to Concider, yet appears some other folks are apparently One-Dimentional thinkers or perhaps suffer from the "not invented by me syndrome " - or perhaps they are indeed 100% always correct and improvements of even say 21.25% would be of no interest?

Less glory and no medals or front page news....

Yet, Inventors and Innovators do incremental work to sectionalize a challenge, often failing, and then trying another approach....somtimes gaining ground and sometimes not....they reverse engineer and think outside the box and sometimes off-the-grid entirely...more losses than wins - but somethings they hit paydirt...

So keep the ideas following and if " you are-not taking flak, then you are-not over the target"....

Perhaps we are stumbling on "something sensitive" and the cann't-doers or otherwise do-not want us to go down these paths of reasearch - hummm - unlikely but pausable....

Bring solutions / concepts - not just can never-ever be improved upon ever.....in my one-sided and baised opinion...

And ask yourself: What have you done or tried to do to improve our Hobby? ( and really don't want your response as just a retorical question for us all...)

Finally - if you are indeed Happy and Content with the Status Quo and do not want or care about improve possibilities, then why bother even responding - or is it just QRM and ZBK-2 ?

Bill

 

[slicerwizard]

Perhaps we are stumbling on "something sensitive" and the cann't-doers or otherwise do-not want us to go down these paths of reasearch - hummm - unlikely but pausable....

Or perhaps you're just delusional - and a terrible speller, BTW. Your "maybe we need GPS receivers in scanners" idea shows just how unqualified you are to make any technical judgments. Honestly, I have to ask if you and James are Dunning–Kruger candidates?

And ask yourself: What have you done or tried to do to improve our Hobby? ( and really don't want your response

Of course you don't. Unlike you, some of the posters in this thread have made significant contributions to the hobby.

Finally - if you are indeed Happy and Content with the Status Quo and do not want or care about improve possibilities, then why bother even responding

Lovely straw man you have there; be sure to keep it away from flames or logic. God forbid that anyone who wants to see LSM improvements should point out when others are blindly stumbling down dead end paths.

 

[MTS2000des]

my point is WHY should I or any owner of a brand new product advertised as supporting P25 have to modify, accessorize or reverse engineer something to get it to do what should be it's basic functionality?

CQPSK-LSM has been part of the P25 standard since the late 1990s. Uniden should know after not ONE, TWO but now THREE generations of their digital scanner product that the traditional discriminator tap design DOESN'T WORK for reliable reception of CQPSK-LSM modulated signals.

They should know by now that no amount of DSP tweaking can overcome bad data being fed into the vocoder. They should know that other manufacturers incorporate I/Q to get good, clean data to feed to the DVSI chip. If not, then it is time to fire their engineering department and hire some who are competent and experienced in designing modern digital RF devices.

A consumer should not be FORCED to make complex changes to an off the shelf product to get basic, solid performance of an advertised feature. If this were a car advertised as getting XXX MPG and it only gets YYY, then you would complain (and rightfully so) and probably want to seek legal action against that automaker. Oh wait, looks like that's already happening:

MPG Fraud - McCuneWright, LLP - Attorneys at Law

Reliable, consistent reception of P25 is why we are buying these scanners. The fact is Uniden knows, or should have known, that their product has a hardware design flaw, and their remedy should be to correct it at the hardware level.

Their history says they will unlikely do so because re-engineering a product would cost a fortune, not to mention a recall campaign would cut too far into their profit. Look at how well they are handling the "headphone gate". Pathetic. Just pump out more poor performing mediocre product at premium prices and people will buy it. That is America. No one cares about quality anymore.

 

[slicerwizard]

my point is WHY should I or any owner of a brand new product advertised as supporting P25 have to modify, accessorize or reverse engineer something to get it to do what should be it's basic functionality?

Of course we shouldn't have to, but this thread is about "I can't wrap my head around how a CQPSK signal is badly handled by an FM demodulator wrt translating +/-45 and +/-135 degree phase shifts into 4 discrete audio levels suitable for dibit extraction, so I think a better timing reference on the RX side will magically fix that particular problem as well as undo the timing slews that simulcast and multipath impart to the RXd signal", so you're off topic dude.

The late Bill Cheek lamented Uniden's propensity for sizzle over steak and we're seeing it in spades. I saw in some other thread that the newer models still have a P25 Waiting Time setting; is that true? If so, that's utterly ridiculous and just another indicator of how badly Uniden is failing at digital. Say it ain't so.

 

[whsbuss]

The late Bill Cheek lamented Uniden's propensity for sizzle over steak and we're seeing it in spades. I saw in some other thread that the newer models still have a P25 Waiting Time setting; is that true? If so, that's utterly ridiculous and just another indicator of how badly Uniden is failing at digital. Say it ain't so.[/QUOTE]

Yep P25 Waiting Time is still there and alive. Just amazing.

 

[Alliance01TX]

size 17 shoes on the way.....

Sir Humor Follows

Your Shoes (sized to fit) are on the way....via Ice Breaker

Hope they fit well too as these forums are indeed at times One Size Fits all it appears....Humor!

Must have struck a sore point as anyone that goes to the length of such a thing as spell checking is looking only to point out anything to make themselves look and feel important.

And you are correct - only posters perhaps with more-than 2,000 post have ever made any contributions I suppose and never a spelling or grammar errors....did you find the three mid-spelled words I put in to test your reading comprehension on Pondering an idea - not saying an answer was available.

Thanks again for your insights and abilities as without same we would be lost..you should be a Beta Tester as Clearly you would have found these issues and made a Product that we would not have this discussion on that just ended in Humor.

 

[PiccoIntegra]

I saw in some other thread that the newer models still have a P25 Waiting Time setting; is that true? If so, that's utterly ridiculous and just another indicator of how badly Uniden is failing at digital. Say it ain't so.

It actually gets worse then that... read my post about their new squelch table solution.. mind boggling. They're trying to fix this by holding the squelch open consistently.

 

[Alliance01TX]

Agree with your comments and I only have the HP-1 and must also go to Full Open just to get an OK reception...hence my impossible quest to se if any possible improvement could be used as a work-around to gain another 25% (just a number) better signal without going to a Yagi...

I understand the coding issue as Max made it clear in another post ... was a great post..as I am not a P25 SME...

Thanks

 

[jcardani]

I agree that Uniden's work arounds are a big joke. Slicerwizard you are right that the hardware needs to be re-designed and they had the perfect opportunity to do it in the X36 models but failed.

I truly believe that are two solutions here. The first is to design and implement an add-on board using either DSP or CML Micro chips that re-modulates CQPSK to C4FM that can bypass the radio's last IF.

The other would be to build our own software (maybe using SDR) that would incorporate correct handling of CQPSK for P25 and also add support for DMR, NXDN, conventional and trunk following, and even the proper handling of narrowband 12.5 KHz with 2.5 KHz deviation audio levels.

I am willing to start a project if I have help in collaboration of ideas and coding. I would put it up on Github or similar. Just let me know.

 

[jcardani]

Hi Pico,

I just read your post. I am thinking that we are in the twilight zone. Unbelievable.

It actually gets worse then that... read my post about their new squelch table solution.. mind boggling. They're trying to fix this by holding the squelch open consistently.

 

[Alliance01TX]

Thanks Joe and perhaps someone can offer to look and those solutions you pose as my hope was to spur ideas and perhaps get the Next Gen folks looking at various methods, which some have outlined prior..

Funny a few years ago SDR was thought to never be available due to cost and compute power - now for $20 you get a USB and free software..

Thx

Bill

 

[jcardani]

I can't take credit for #1, that was mentioned by KA1RBI a few months ago. I was just pushing the idea further.

Thanks Joe and perhaps someone can offer to look and those solutions you pose as my hope was to spur ideas and perhaps get the Next Gen folks looking at various methods, which some have outlined prior..

Funny a few years ago SDR was thought to never be available due to cost and compute power - now for $20 you get a USB and free software..

Thx

Bill

 

[JamesO]

This as usual cracks me up.

Agree that a better and more robust receiver/demod would have been the best solution. But this does not appear to be what was delivered, so what are we the end users to do?? Sit on the sideline and complain or EXPERIMENT and see what, IF ANY, incremental improvement(s) can be made and if there are realistic to implement.

But again, some FAIL to follow my logic and idea.

Given the demod is not ideal, my point was the non ideal demod could very well benefit from a more stable base clock source to reduce phase jitter/drift as well as overall receiver frequency tolerance and drift.

A non ideal demod needs all the help it can get on the RF baseband side.

Additionally I have not observed for sure how signal level variations during a transmission might cause the spinning toilet bowl effect. Although the P25 is transmitted on a FM carrier/signal that in theory should be mostly immune to signal level variations, one might be surprised to see what happens in the real world.

So maybe if Uniden was able to get the AGC working and give a description on all the settings and how and why one would choose these settings this may also improve the P25 signal decoding quality. You can only do so much post demod processing, but you will can only squeeze so much blood from a turnip. Ideally you want accurate and stable data to begin with.

I agree that when you by a $600 radio you should not need to modify it to perform better and Uniden should have really done a better job on the demod section, but this did not happen. It is like someone buying a new $50k car and deciding it does not perform well enough and modify the engine, brake, suspension and tires. Someone personalizing the vehicle but also improving the performance if performed in a proper manner.

Maybe a radio with a decent front end and demod section can be far sloppier, but maybe the Uniden implementation can be improved with a better time base.

Very easy for all the keyboard technicians here that play with SDR and say nothing will work. If you ever had your hand on the basic building blocks of receivers, synthesizers and mixers you might understand that the total system performance is limited by the base reference clock and the first state amplifier in the system.

But I can tell we have plenty of forum members here that have all the answers and know that all of these basic suggestions are a total waste of time and effort, too bad they just can't keep their comments to themselves and let the court jesters figure out on their own that NOTHING will improve matters except for a complete and total redesign from the ground up of a totally new receiver platform, or just put a $30 SDR USB dongle and an old $30 Android phone in a box with rechargeable batteries and have a "real" radio.

 

[PiccoIntegra]

Agree with your comments and I only have the HP-1 and must also go to Full Open just to get an OK reception...hence my impossible quest to se if any possible improvement could be used as a work-around to gain another 25% (just a number) better signal without going to a Yagi...

Your observations on the HP1 should tell you immediately that the problem isn't with any timing mechanisms at all. Symbols can be recovered in software without any timing reference of the site controllers themselves. But you have to have the right hardware to do it. There is no way to fix this without a complete redesign of the radio. Once the right hardware is in place, you then need some cleaver software to take advantage of said hardware.

Uniden's biggest problem has more to do with how they process the incoming signal. They're using a 4 level slicer to try and recover symbols. There may be some hardware and software filtering. But it's all for naught on complex digital demodulation.

On all the BCD models, there is an APCO error display with other useful info. Here is a graphical plot of the threshold values while on a LSM control channel.

It's pretty self explanatory what is happening here.. mesmerizing, isn't it?

I understand the coding issue as Max made it clear in another post ... was a great post..as I am not a P25 SME...

Max is a very smart fellow, and so is slicerwizard. You shouldn't be so dismissive of his opinions.

 

[grem467]

Although the P25 is transmitted on a FM carrier/signal"


THATS the problem. LSM is not pure fm. There are phase and amplitude components that an FM discriminator simply cannot respond to. This is why you can't fix it in firmware. It's not a time base, jitter or software issue, it's the hardware simply strips critical parts of the signal, driving the bit error rate up to the point where decode can be problematic.

 

[PiccoIntegra]

The first is to design and implement an add-on board using either DSP or CML Micro chips that re-modulates CQPSK to C4FM that can bypass the radio's last IF.

You'd be better off using the old GRE based receivers of the nineties. Those radios were modular in their design. You could probably control the RF section with an Arduino. The schematics for all those radios are also freely available online. Without one, you're pretty much dead in the water. In the unlikely event you obtained one for a Uniden radio, you would still need to make changes in the firmware. It is hackable however..

The other would be to build our own software (maybe using SDR) that would incorporate correct handling of CQPSK for P25 and also add support for DMR, NXDN, conventional and trunk following, and even the proper handling of narrowband 12.5 KHz with 2.5 KHz deviation audio levels.

SDR# made some changes to their plugin code recently. Those changes open up a huge opportunity for scanner type functionality via SDR hardware. Things are going to get interesting real soon...