BCD325P2/BCD996P2: Simulcast distortion fix

[masterknowitall]

Has anybody heard of possible chance that Uniden might magically create new firmware to help or resolve simulcast distortion on a BCD996p2?
So many are posting their frustration on here but usually the same recommendations that work for some won't work for all.
There has to be a fix. Does Uniden ever look in these Uniden Forums?
I resign myself to sit here, with a silent scanner, hoping for a realistic fix.

I'm hoping, not whining and just frustrated.

 

[wscranston]

It's a hardware cum mathematical issue, not a software issue.

 

[Markb]

The technology/hardware in the 996 will not allow a fix. It has to do with 2-level vs. 4-level decoding. Kinda like 2D vs. 3D.
The 996 can only decode in 2D and 3D is needed to overcome SC distortion (overly simplistic example).

The whole selling point of the SDS series is that they are software-based, and have the -4-level decoding capability, although the 2 are not mutually inclusive. In other words, they had to design a whole new radio to overcome simulcast distortion. If it was a firmware fix, they would have addressed that a long time ago.

 

[waterbwuk]

Unfortunately the only realistic fix is to buy an SDS. As far as I know that's the only thing on the market that can handle simulcast. I've got some SDR's that handle it "OK" for the most part (it's really the software that handles it, SDRTrunk), but it definitely has days where it's so distorted you can't make much out of what is being said.

There's a good video floating around here where someone covered a couple of different things to help with distortion. I can't find the link, but maybe someone will post it. In my situation, I was under the impression that I needed a better antenna when it was the complete opposite. I actually took steps to reduce the signal quality and the audio got better. Sometimes I just run the SDR's with no antenna at all and it works, somehow.

 

[trentbob]

Has anybody heard of possible chance that Uniden might magically create new firmware to help or resolve simulcast distortion on a BCD996p2?
So many are posting their frustration on here but usually the same recommendations that work for some won't work for all.
There has to be a fix. Does Uniden ever look in these Uniden Forums?
I resign myself to sit here, with a silent scanner, hoping for a realistic fix.

I'm hoping, not whining and just frustrated.

NO

 

[Ronaldski]

Take a look at

Even mention using a metal cake pan, etc.

 

[btt]

This is a nice presentation that may help in understanding the simulcast distortion issue. This is a presentation I ran across while searching in the past. I'm not associated with it in any way. To the receiver, multi-path propagation and simulcast distortion look the same. Multiple signals arriving at different times due to taking different paths from the transmitter to the receiver. This causes phase smearing. Decoding the signal in quadrature and DSP techniques in software can enable a receiver to deal with the issue of delay spread much better than legacy peak detector / M-FSK slicers.

https://www.wirelessinnovation.org/assets/Proceedings/2011/2011-6b-taylor-presentation.pdf

 

[jaspence]

Sometimes simulcast can be a simple location or antenna change, but not a sure fix and a few inches move in the wrong direction changes the reception.

 

[iMONITOR]

@masterknowitall

PM SENT

 

[W1KNE]

Sometimes simulcast can be a simple location or antenna change, but not a sure fix and a few inches move in the wrong direction changes the reception.

Atmospherics and changes in the conditions of the amplifiers themselves also are uncontrollable variables.

 

[masterknowitall]

@masterknowitall

PM SENT

Thanks

 

[masterknowitall]

Thanks

Got it. Thanks

 

[stlouisx50]

In my county the EMS repeaters towers cause one hell of a distortion. To the point the signal totally fades out. That's on regular VHF. As others have said you can change antenna locations or use some foil to block multiple signals, but you will have to do lots of testing. Note that you may block other signals that you may want to hear.
The real issue is mobile. You can't really block a signal since it's always changing. Sometimes putting it in the center of the car works better or by the door panel. I wonder if an inline type filter would work? ATT may or may not help. Never been a fan of it.

 

[n1chu]

…I’ve always been of the opinion that in order to eliminate distortion on the same transmission being transmitted from more than one site, the sites would be slightly out of sync with each other (due to differing distances from each site which causes the transmissions to reach the scanner at differing times) it would be necessary to turn off all but one site. And as it has been stated, while mobile, it’s hardly practical because now the scanner is moving which causes the distances between the sites and the scanner to change. Switching the sites received on and off manually is called distracted driving. A comparator of sorts would be needed to measure and pass along a good quality signal while ignoring the rest. This operation would be handled automatically, hands stay on the steering wheel. Is this how the commercial trunked mobile radios work? A comparator within each mobile unit? Or do the the mobile units send GPS location data to the controlling computer and that computer determines the routing? Or maybe something else? I am somewhat knowledgeable of what to expect from a trunked system but not how they make them work. Anyway, I’ve never had an issue with simulcast. I’m told the Ct. State Police trunked system, known as CLMRN (Ct. Land Mobile Radio Net) is a simulcast system but I have never had a problem with it… maybe it’s not the type of simulcast that causes the problem.

 

[900mhz]

…I’ve always been of the opinion that in order to eliminate distortion on the same transmission being transmitted from more than one site, the sites would be slightly out of sync with each other (due to differing distances from each site which causes the transmissions to reach the scanner at differing times) it would be necessary to turn off all but one site. And as it has been stated, while mobile, it’s hardly practical because now the scanner is moving which causes the distances between the sites and the scanner to change. Switching the sites received on and off manually is called distracted driving. A comparator of sorts would be needed to measure and pass along a good quality signal while ignoring the rest. This operation would be handled automatically, hands stay on the steering wheel. Is this how the commercial trunked mobile radios work? A comparator within each mobile unit? Or do the the mobile units send GPS location data to the controlling computer and that computer determines the routing? Or maybe something else? I am somewhat knowledgeable of what to expect from a trunked system but not how they make them work. Anyway, I’ve never had an issue with simulcast. I’m told the Ct. State Police trunked system, known as CLMRN (Ct. Land Mobile Radio Net) is a simulcast system but I have never had a problem with it… maybe it’s not the type of simulcast that causes the problem.

Think about this...authorized radios on a trunked system have a distinct advantage over a receiver of any type. Remember those radios communicate with the respective tower sites. Not to burst your bubble, but the 996P2, although a very nice radio, does not perform satisfactorily in simulcast environments. While they may work, there are times where it bites the dust. Yes band conditions can change, even on the 700/800 band. SDS, or even better in every case, a Unication G4 will beat the pants off a 996P2 on 700/800 MHz P25 systems I have encountered, including the State of CT. I don't consider antenna compromises (paper clips, and other such behaviors) in order to receive a signal acceptable.

 

[GTR8000]

…I’ve always been of the opinion that in order to eliminate distortion on the same transmission being transmitted from more than one site, the sites would be slightly out of sync with each other (due to differing distances from each site which causes the transmissions to reach the scanner at differing times) it would be necessary to turn off all but one site. And as it has been stated, while mobile, it’s hardly practical because now the scanner is moving which causes the distances between the sites and the scanner to change. Switching the sites received on and off manually is called distracted driving. A comparator of sorts would be needed to measure and pass along a good quality signal while ignoring the rest. This operation would be handled automatically, hands stay on the steering wheel. Is this how the commercial trunked mobile radios work? A comparator within each mobile unit? Or do the the mobile units send GPS location data to the controlling computer and that computer determines the routing? Or maybe something else? I am somewhat knowledgeable of what to expect from a trunked system but not how they make them work. Anyway, I’ve never had an issue with simulcast. I’m told the Ct. State Police trunked system, known as CLMRN (Ct. Land Mobile Radio Net) is a simulcast system but I have never had a problem with it… maybe it’s not the type of simulcast that causes the problem.

How would you "turn off" or "ignore" a subsite in a simulcast cell, when they are literally all transmitting the 100% exactly identical RF? It's physically impossible and cannot be done, there is nothing in the RF that distinguishes one subsite from another, that's the entire point of a simulcasted signal.

Real subscribers are designed to handle the slightly out-of-phase signal that is inevitable in areas of simulcast overlap. It's actually not rocket science, it just requires the proper design of the receiver to make sense of it all. There are no fancy tricks like GPS on the subscribers, as again, that wouldn't do any good when there's no ability to differentiate between subsites regardless.

 

[GTR8000]

Think about this...authorized radios on a trunked system have a distinct advantage over a receiver of any type. Remember those radios communicate with the respective tower sites.

That doesn't really factor in when dealing with a simulcast cell. To even an "authorized radio", it appears as a single site, and is blind to the subsites that make up the cell. Think of it as one virtual site comprised of multiple physical sites (aka subsites), that is what a simulcast cell is. Affiliating with the system or not, it makes no difference. Either the hardware was designed to properly demodulate the signal, or it wasn't. Plain and simple.

A $700 Unication G series pager can receive a simulcast cell just as well as a $5,000 APX that is affiliating, because the Unication was designed correctly.

 

[900mhz]

That doesn't really factor in when dealing with a simulcast cell. To even an "authorized radio", it appears as a single site, and is blind to the subsites that make up the cell. Think of it as one virtual site comprised of multiple physical sites (aka subsites), that is what a simulcast cell is. Affiliating with the system or not, it makes no difference. Either the hardware was designed to properly demodulate the signal, or it wasn't. Plain and simple.

A $700 Unication G series pager can receive a simulcast cell just as well as a $5,000 APX that is affiliating, because the Unication was designed correctly.

But it does in relation to the talkgroup, and the authorization of that talkgroup on certain sites.

 

[fredva]

…I’ve always been of the opinion that in order to eliminate distortion on the same transmission being transmitted from more than one site, the sites would be slightly out of sync with each other (due to differing distances from each site which causes the transmissions to reach the scanner at differing times) it would be necessary to turn off all but one site. And as it has been stated, while mobile, it’s hardly practical because now the scanner is moving which causes the distances between the sites and the scanner to change. Switching the sites received on and off manually is called distracted driving. A comparator of sorts would be needed to measure and pass along a good quality signal while ignoring the rest. This operation would be handled automatically, hands stay on the steering wheel. Is this how the commercial trunked mobile radios work? A comparator within each mobile unit? Or do the the mobile units send GPS location data to the controlling computer and that computer determines the routing? Or maybe something else? I am somewhat knowledgeable of what to expect from a trunked system but not how they make them work. Anyway, I’ve never had an issue with simulcast. I’m told the Ct. State Police trunked system, known as CLMRN (Ct. Land Mobile Radio Net) is a simulcast system but I have never had a problem with it… maybe it’s not the type of simulcast that causes the problem.

You can't turn off a site that is simulcast. A simulcast site = multiple transmitters using the same frequencies. Those transmitters are essentially identical, so your scanner is unable to filter out any of the transmitters within the site. The only "filtering" that can be done is through a directional antenna or some kind of attenuation that weakens signals from transmitters that are farther away. But that's tricky to do.

 

[fredva]

But it does in relation to the talkgroup, and the authorization of that talkgroup on certain sites.

I think you are talking about a multi-site system, which is a completely different animal than simulcast.