Official Bucks County 700Mhz Phase II Radio System Thread

[APX_Radio]

Simulcast - The RadioReference Wiki

 

[radicalbill]

Thank you - and a question

My error rates go from 2% to 40%, all within the same transmission. I am guessing the signal strength is fluctuating, but I don't why, since the antenna is not moving.

If the 2nd tower has a weaker signal, the 1st tower should be overpowering the weak signal, right ?

I have a 30 foot hill directly in front of me, where the antenna needs to point to get to the closest tower, which is 2 miles away.

The other tower is 4 miles away, but the land obstruction is about 2 miles away.

I am thinking aiming the antenna in the opposite direction towards that tower might give a better signal, but I may be in a "Dead Zone" where I won't get a reliable signal no matter what I do.


I noticed that the freq of the control channel I am getting is one of the alternates, and not the same freq as someone else posted they were getting, that was not the primary freq either.

That is what made me think they were using different freqs from different neighboring tower sites.

The terrain here is pretty tough for type of system.

There are some dead zones, I hear them talk about them when they switch to the VHF backup channel.

Any thoughts ?

Thanks

Bill
KC2OVX

 

[phillydjdan]

They all use the same frequency. They "simulcast" the signals off all the towers. It works by delaying the signal by a fraction of a second so that a receiver would not pickup the signal from 2 or more sources at the same exact time. The dispatch channel is now the same way. All towers transmit the same voice, just timed ever-so-slightly off that it doesn't knock the adjacent signal out.

 

[radicalbill]

Doesn't distance to the source reduce time ?

If you are closer to one tower, say, right next to it, the time for the signal to reach you is going to be less than if you were 2 miles further away.

Is it actually transmitting multiple data streams of exactly the same data ?

So, the radio has to figure out that the data it is getting is duplicate and ignore it ?

Sounds really complicated.

Why do they do this ? It seems using separate freq's for the control channel would make sense, a lot more sense.

Just my thought.

Seems like a lot more room for error

 

[phillydjdan]

Exactly, and that's why the scanners don't work well on simulcast systems. The receiver circuit isn't designed to receive multiple sources and decipher which one is the best. Commercial radios do. That's why these scanners cut out all the time. It's not that the signal is too weak, it's that 2 sources are knocking each other out. They design systems like this because for the subscriber radios it works out very well. The drawback is that it does not for scanner users. But as they will tell you, these systems are not built for you, they're built for the subscriber radios.

 

[radicalbill]

Sounds like the Yagi is my best bet to get a clean signal

It sounds like the yagi is the best bet for me, since it limits the signal coming in from the second source.

I wish there was a way to see which tower I am getting a stronger signal from.

Does Unitrunker or any of the other software decoders show which tower it is receiving ?

I don't remember ever seeing anything like that in the software.

The scanner say the SID: 04D3h-0101

I am guessing every tower send out the same data, making it impossible to know which tower I am actually getting.

I will have to do some more work. I ordered two 700 Mhz antennas, one is a 9 element, the other an 11 element.

I don't know if they will work better than my Wilson 800/900 yagi.

That worked where all the other yagis I have did not.

All the others were from China, and worked better in NY for the 800 band than the Wilson did.

Glad I kept the Wilson.

Bill
KC2OVX

 

[phillydjdan]

A yagi will definitely help. When this whole simulcast distortion issue first cropped up for me I had done numerous experiments and found the best results with a yagi. And it was even a cheap $30 5 element one. Still use it for Philly to this day. The towers all transmit the same data, so Unitrunker won't help you figure out which one you're hitting off. What I did (and this is nowhere near exact) was put my smartphone's GPS on and literally stood next to the yagi pointing my phone in the direction the yagi was pointing. That allowed me to sort of loosely figure out which site I was pointed at. It also helps to just leave the bolts loose enough so you can turn the yagi. Just turn it a tad bit and watch your signal until you dial in the best quality.

 

[chetp]

It's not what direction to aim the antenna.....it's turning checking, turning checking....the best direction probably won't make sense!

 

[radicalbill]

Thanks for the help

I will get up there and try to get it pointed so I get the best signal.

I will try the 700 MHz antennas to see if they are any better.

They are waiting at the post office to be picked up, so maybe Tuesday I will get to them.


I did notice that dispatch always sound clearer, and has lower, or no errors, while the mobiles and portable have higher errors and sound worse.

Also noticed some talkgroups have lower errors and sound better than others.

Not sure why that is.

Thanks

Bill
KC2OVX

 

[trentbob]

Hey Dan, I haven't been on RR for a long time, of course you would know better than anyone why but I wanted to take a look at your thread to see if anything is new. It looks like the same old questions and problems with the same answers. I give you a lot of credit brother. The system is been sounding good. No dead spots anywhere and I was out in Princeton last week and the Bucks system was banging in. I have been using the 800 stubby exclusively now as it works very well with the BURCO uhf T Band too. Well, talk to you on the other side, I was very surprised to see you on here again. You are the man to help the guys out with radios that don't perform as advertised. Later.

 

[trentbob]

Yeah Dan I agree regarding our text conversation... just some info for you guys trying to pick up the the new Bucks system. Dan and I did a lot of research when the system first came out including a video. Before you spend a lot of money on antennas keep in mind no matter what you do it won't work well unless you are lucky that your fixed position is just right as regard to your position between towers. In a mobile application it will not work at all. You might think it does but you're missing a lot of transmissions. Remember because of the nature of LSM you will get better results with less efficient antennas that will only pick up one tower at a time. Rooftop antennas are the worst unless you use a directional beam pointed at the closest tower. They only work if you're lucky and again it depends on your location to the towers. As the professionals know if you need a dependable radio for Bucks for your employment as I do the only way to go is a professional subscriber radio as I do (APX7000). Good luck everybody, 73's... Bob.

 

[radicalbill]

I just started logging today and I am getting data that does not match

I have the radio set just for Zone 7, TGID 8.

I am seeing uid numbers that are all 7 digits long.

They all start with 436, not sure why they do that, maybe someone has information on this,

but what I am seeing for the last 4 digits does not match what is in the wiki.

I am seeing 2233, lots of traffic on that uid

then the uids that are on this TG are

27xx
34xx
35xx
36xx
37xx
40xx
41xx
9964 lots of traffic on this, this is the dispatcher
9970
2058
2039
2000

All these start with 436

I am thinking some of these may be from outside the zone, but the others, I don't know

I just hooked up the recording cable, so now hoping to get some unit ID's to go with the uid numbers.

the only one I see so far and have heard is 3616 and that is 59-17

I am hoping someone has a sheet that tells what zones each dept has, so if all the 36xx match to zone 59, and so on, that would be real helpful

I have 40 uid's so far, and I am thinking some of these are portables

Not sure if anyone has the numbering system for what radios are portables and what radios are mobiles.

Anything would be helpful.

It looks like the wiki needs a lot of updating, and I am hoping to get at least this zone updated.

Not sure if I could do all of the zones. It takes a lot of time, and the uid does not always come up, so that makes it even harder to figure out, plus dispatch rarely gives the actual unit ID, so doubly hard.

But, I will work on it.


I heard a call today for where I live, which is why I bought this radio to begin with.

Seeing all the police racing in and out, almost every day, I would like to know what is happening in my neighborhood.

Thanks

Bill

 

[feedus]

I know that they did have to reprogram the FD radios at our station as part of an upgrade. What they did exactly, I don't know. Maybe the police side had an upgrade too.

 

[radicalbill]

Here is what I got today

This is very preliminary, but at least it gives you an idea of what I am getting.

There is some order to it, with certain units having groups of uid's that are all in the same range.

I am looking for what each group belongs to. Like the 36 units, the 58 and 59 units, etc..

Since this zone covers different towns, and some towns have their own police, that are on the new system, I see the dispatcher using different uid's to talk to some of the units.

I have not had time to study it in more detail, and this is only a few hours worth of monitoring, and the radio does not always display the uid, and I don't know why that is.

But, if anyone has done more logging, or knows what units go where, please reply.

In the mean time, take a look at my XLS sheet and see if you can offer any help.

Thanks

Bill

 

[radicalbill]

More info on uid's

A pattern is starting to develop, but still no idea what units go where.

Someone, somewhere, must have a list, like the FD districts have a list, that tells what units cover what areas.

It looks like there are 2 radios for each unit, but I can't tell which ones are the mobiles and which are the portables.

If anyone has a list of the units, and what areas they are out of, that would be really helpful.

I know there is some overlay of districts, where there is double coverage, or even triple coverage, but just a basic guide to go by would be really helpful.

Also, if there is some program, other than freescan, that will get all the uids, that would help.

I am thinking trunktracker might do it, but if there is something else that is better, please tell me.

I have an SDR that I can use to get the UID's, but I don't know how to log them using trunk tracker and if there is a way to do just one zone, that would help too.

I am attaching the latest revisions to my XLS file

Any input would be great.

I would like to start a new wiki page with the new systems info on it.

Thanks


Bill

 

[wb3ayt]

BCD436HP and missing Bucks Talk Groups

Hi All,

(I've read this thread through and followed it since September. My compliments to Dan and others who help everyone here on this challenging system.)

I'm wondering if I'm missing some configuration detail in my BCD436. I receive all PD zones very well. However, the only FD/EMS Talk Group I receive is Dispatch. I have verified that all FD/EMS tg's are Not avoided.

Point of reference... I work very near the Ivyland tower and find my PSR800 does very well there on my desk (as opposed to while mobile or at home in Doylestown/Warrington where reception is very broken) and receives all FD tg's.

With the BCD436 right next to the PSR800, I still only receive the FD/Dispatch and no others.

I've been through the manual repeatedly and have not yet found any obvious cause.

Does anyone have any ideas if my BCD436 setup is the problem?

Thank you in advance!

-Don

 

[phillydjdan]

If enabling the "Fire Talk" service type does not help you I don't know what the problem could be.

 

[wb3ayt]

Thanks, Dan. That's it! I just couldn't come up with the term 'service'.

Again, thanks for all you do here.

-Don

 

[radicalbill]

TG 44 ?

I don't see this group in the list on the wiki page, but I am seeing it in the Unitrunker.

Any idea what TG 44 is used for ?

Thanks

Bill

 

[radicalbill]

TG 49 also

I just saw this TG too. This is brand new. Never seen it before.

I will have to look at the logs and try to figure out what uid's are connection to it.

Thanks

Bill