The official "I want LSM to work properly in my scanner" thread

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APX8000

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LSM reception deals with several variables....one of them being where you are located in relation to the towers. I’ve had Unitrunker running through a PSR-800 and I can watching the signal drop from full bars to nothing just by moving it a few inches on my desk. Makes for mobile scanning nearly impossible on several systems.


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fredva

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I've been told here in Michigan, our Motorola P25 Simulcast system uses CQPSK (NFM) modulation. Might that explain why I'm not experiencing any problems or frustrations monitoring them using Uniden's BCD996XT, and BCD996P2 scanners. Whistler and most Radio Shack (aka GRE) scanners have worked well for me as well. Macomb County's simulcast system consist of 9 towers, and soon to be more.

Are those scanners stationary or do you use them mobile?
 

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Are those scanners stationary or do you use them mobile?

They're all stationary in my home office using Radio Shack RS-800 antennas. I tried a PRO-106 with a RS-800 inside of my SUV sitting in a cup holder and reception was usable.
 

slicerwizard

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Going by facts. CQPSK signals are both amplitude and phase modulated. Phase modulation is essentially frequency modulation, but an FM receiver will not recover CQPSK's amplitude component. CQPSK is not an FM signal, which is a large part of why an FM receiver doesn't properly handle it.

Top: frequency component of CQPSK signal

Bottom: amplitude component of CQPSK signal
 

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fredva

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They're all stationary in my home office using Radio Shack RS-800 antennas. I tried a PRO-106 with a RS-800 inside of my SUV sitting in a cup holder and reception was usable.

Ok, sounds like you're one of the people who happen to live in the right spot to get a good decode on simulcast. But once you move around, it's not so great.
 

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Silent Key
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Going by facts. CQPSK signals are both amplitude and phase modulated. Phase modulation is essentially frequency modulation, but an FM receiver will not recover CQPSK's amplitude component. CQPSK is not an FM signal, which is a large part of why an FM receiver doesn't properly handle it.

Top: frequency component of CQPSK signal

Bottom: amplitude component of CQPSK signal

I'm in no position to debate this, it's all way over my head. I appreciate your input.

I wonder why I have such success monitoring this system from my home. I do have friends that don't do as well. One is about five miles N-W of me. I have found a minimal antenna, surrounded by two vertical metal vertical computer towers works perfect. Possibly acting to some degree like a corner reflector antenna?
 

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Ok, sounds like you're one of the people who happen to live in the right spot to get a good decode on simulcast. But once you move around, it's not so great.

That sums it up pretty good. However, I can move around within my home with no real ill effects.
 

KR7CQ

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That sums it up pretty good. However, I can move around within my home with no real ill effects.

Within your home is effectively the same position. If you change your position so that you are halfway between two sites, you will see the problem. Likely, you are either quite a bit closer to one site than others, or all but one site is obstructed in some way, or both. I'm in the same situation at work. I sit right under one of the towers, and any digital scanner will yield 100% decoding of the Phoenix simulcast system. From my house, or much worse yet on the move, a scanner is worthless. I often joke that cops on trunked P25 systems don't really need encryption, most scanner users can't hear what they are saying anyway lol.

Simulcast hell occurs when you are right in between two or more sites. Scanners can't make sense of the signals coming in at (very slightly) different times, at a similar signal strength. To be on the move and hear everything in a simulcast system requires a commercial radio or a Unication G4/5 as far as I can tell. I can toss my G4 on the floor of my car with the 1" long stubby antenna and monitor a simulcast system perfectly. Unication seems to have figured this issue out. Now if only scanner companies would figure it out...
 

fredva

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After setting up and running a Raspberry Pi with an SDR dongle and OP25, it's been proven to me that the solution to LSM is having the right demodulator for CQPSK. OP25 using the CQPSK demodulator and an omni-directional antenna gives clear decoding on two local simulcast systems, better than my 436hp hooked to a directional antenna. The Pi setup doesn't have all the features of a scanner, but for roughly $70 worth of equipment (not counting antenna), it does pretty well.
 

APX8000

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It still amazes me that with a huge migration of systems towards LSM that scanner companies haven’t come up to speed.


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scanmanmi

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Can any of you techies figure out why?

It still amazes me that with a huge migration of systems towards LSM that scanner companies haven’t come up to speed.

Amen. Would the mfgs have to abandon all their circuit designs and start over? Is it a legal or copyright issue (maybe Unication pays somebody)? I don't give a rip about wifi or remote access, color LCD screens, flashing lights, recording, zip codes, I JUST WANT A RECEIVER THAT WORKS! I refuse to buy a new one until this is fixed.
 

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Amen. Would the mfgs have to abandon all their circuit designs and start over? Is it a legal or copyright issue (maybe Unication pays somebody)? I don't give a rip about wifi or remote access, color LCD screens, flashing lights, recording, zip codes, I JUST WANT A RECEIVER THAT WORKS! I refuse to buy a new one until this is fixed.

Why not sell all your scanners and buy a Unication? Listening to the user community the problem has been solved!
 
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belvdr

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Why not sell all your scanners and buy a Unication? Listening to the user community the problem has been solved!
Likely because they don’t work exactly like scanners, such as scanning more than one system.
 

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Likely because they don’t work exactly like scanners, such as scanning more than one system.

I agree 100% That's why I haven't bought one myself, and I remain content with my three Unidens. Over the years I have found simple little things that make them work better with Simulcast systems and for the most part I'm satisfied. That's not to say I'd like them to be better, but as the saying goes, as bad as scanners are, they're the best we got!

I started with simple 8 channel scanners that used crystals. As technology advanced/improved I kept pace with it by selling what I had, and buying the latest and the greatest. Yes there were growing pains along the way, but that goes with the hobby. Many of the people complaining about today's newest scanners don't have an appreciation of what it took to get where they are. If you expect them to perform 100% perfect, you should problem seek out a different hobby. Scanners are a work in progress. As improvements are made, new firmware is usually released. As more significant additional features are engineered, they are made available.

All the complaining in the threads isn't going to change a thing. Uniden, and Whistler can't pull a fix out of their hat. It just isn't that easy. Do you honestly think manufactures just delay things to irritate customers. I think a lot of people do not show Paul and Wendy the respect they deserve. Yet at the same time they try to push them harder and harder for a fix. If they had a fix, you'd have it. If it take more time, and it's possible you get it, but not before. Some people on RR act like spoiled children. Perhaps they are!

belvdr, to be clear I'm not directing this at you.
 

RFI-EMI-GUY

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Going by facts. CQPSK signals are both amplitude and phase modulated. Phase modulation is essentially frequency modulation, but an FM receiver will not recover CQPSK's amplitude component. CQPSK is not an FM signal, which is a large part of why an FM receiver doesn't properly handle it.

Top: frequency component of CQPSK signal

Bottom: amplitude component of CQPSK signal
Any idea what information the amplitude component conveys? Is it strictly for synchronization of the data in the phase modulation? That might explain why an FM demod sort of works up.

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scanmanmi

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I agree 100% That's why I haven't bought one myself, and I remain content with my three Unidens.
Me too. I currently am not in a Simulcast area but I travel through them so I don't take my scanner anymore since I found out.

I started with simple 8 channel scanners that used crystals.
Me too.

Scanners are a work in progress.

They have been working on bells and whistles and upgrades instead of a correct decoder.

All the complaining in the threads isn't going to change a thing.

It will. When they find out we are on to their little game of selling scanners that don't work right they will have to expidite the change. Others will figure out how serious of a problem this is.

Uniden, and Whistler can't pull a fix out of their hat.

Then they should pulll one out of somewhere else.

Do you honestly think manufactures just delay things to irritate customers.
I know for a fact they do. I used to work for a mfg and can guarantee they will do nothing to impede the flow of income. They will not put a little note on the box saying this device is not intended to decode LSM. I am sure they are develoing some kind of product now. My issue is that I am just now finding out about it and they knew years ago. They should have something out already. It's going to have a high price tag and in order to justify the high price they are going to have to cram in a bunch of junk bells and whistles. That goes back to my question above about WHY is it not done already? They keep pumping out radios that don't work correctly.
 
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