Simulcast question - BCD996T

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Airdorn

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Hey all.

I have a 996T and one of the big systems in my area is an 800Mhz standard MOT Smartzone. It is the Memphis/Shelby County Public Safety system in Tennessee.

The frequencies are divided into two sites in the RR database and it is labeled as simulcast.

My question is, do ALL those frequencies have to be entered into the scanner as separate sites under the same system for things to trunk track properly?

What exactly is meant by 'simulcast' ?

Thanks for any info!
 

torontokris

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I think it means the Talkgroups are broadcast over both sites.. so a west police division can hear what an east police division TG even if they originated on different towers.

Not the technical definition I know

From Wiki
"In many public services, radios used by police and fire officials are often simulcasted on multiple frequencies so that other agencies can hear what is going on and what the dispatcher is saying"
 

torontokris

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http://www.radioreference.com/apps/db/?sid=4361

I would program BOTH as separate systems with thier own Quick Key , but thats just me.
That way you can turn one on or off with a quick key if you wanted to.

You can trunk track just only ONE site just fine (as long as you have all the freq from that one site or are using control channel only).

However some people would program it as a multi-site that way you only need to put in the talkgroups once.. and will be followed on both sites.

I maybe wrong but for a simulcast its a personal preference I guess (compared to if it was a true multi-site system).
 

torontokris

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Just found this on the rr wiki..

Simulcast...
Refers to the process of transmitting the same signal from multiple sites.

For public safety communications, this typically means multiple towers configured to transmit the exact same communications, on the exact same frequencies, from multiple towers, resulting in much better coverage of a wide area or area with dense population/buildings.

Retrieved from "http://wiki.radioreference.com/index.php/Simulcast"
 

Airdorn

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DOH! I missed that. Thanks!

I have both sites programmed in a single system. But I think doing it this way slows scanning down. Not 100% sure, though.

I'm going to try just 1 site.

Thanks again.
 

torontokris

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I'm not 100% sure either
so we are in the same boat but I wouldn't think it would slow it down maybe only milliseconds as it jumps sites/ control channels.

Check that your hold/ delay time is set to zero, again on this system may not matter too much

And lastly if you are only going to use one site be sure to program in your closet site/tower.. The one with the best reception. If you travel around the full city you may need both for parts where one site/tower reaches but not the other
 
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Airdorn

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It's really about the idea of simulcast, itself, and how a simulcast system should best be programmed into the BCD996T.
 
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n4yek

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Airdorn said:
It's really about the idea of simulcast, itself, and how a simulcast system should best be programmed into the BCD996T.
I would program each tower site as an individual system, then assign each system the same Quick Key number so when you activate the quick key All individual systems would become active at the same time. It would require duplicating your talkgroups for each site, but this would be the best way to do it.

or

You can do it the way torontokris says and assign each its own quick key so you can turn each site on or off.
 
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tspainiv

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Program them both as two different sites. All public safety (MPD, MFD, SCSO, SCFD, EMA) on the Memphis/SC system is on site 1. All others (public works, hospitals) are on site 2.

All the sites around the county broadcast the same traffic on each tower, at the same time, hence the simulcast. The site 1 and site 2 are not necc. two different sites, they are two different sub-systems, so to speak. Each tower broadcasts traffic for site 1 and 2.

If you really want to find out some good info on the system, or anything else that is comm related to the mid-south area, you should stop by our scanner meeting next Saturday, 31st. See this thread here for more info. http://forum.scanmemphis.net/viewtopic.php?f=4&t=152
 

N1CTF

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A simulcast system is one where all sties transmit the same information in sync, at the same time. Each site is a clone of the others. So, for example, if it is a 10 channel system, with 5 sites spaced about the county, they will all have the same channel 1 frequency, same channel 2 freq, same control freq, etc... The data on the control channel and voice channels is exactly the same, and on the same frequency, at every site. They use GPS for timing to keep everything synced up.

So, you can consider a simulcast system exactly like one large single site. There is no need whatsoever to program each site of a simulcasted group of sites as its own site. Just lump them all together as one larger site and pick a location somewhere in the center of the coverage area for the latitude and longitude, and set the range accordingly.

You can tell if a system is simulcast by looking at the FCC transmitter frequency allocations for each of the sites in question... if they are all licensed for the same group of frequencies, and all those sites overlap just a little, then it is most likely a simulcast system.

It would definitely work better if each site could have its own group of channels, but there are sometimes not enough frequencies available.

Simulcast is next best option, but its not as good because there can be areas where the signals overlap and cause destructive phase cancellation. Motorola and Ma/Com have complicated algorithms in their receivers to combat this problem but don't expect a scanner to perform as well in some of those areas. Especially in digital modes.

One more note: Most wide area networks, like Palmetto, or VIPER 21 are a conglomeration of county-wide simulcast systems. There might be 59 sites listed in the RR database, but each so called "site" is really a group of a few closely spaced simulcasted transmitter locations all operating on the same frequencies to improve coverage. Or it could be just one transmitter location, if the coverage is sufficient. But either way, to program these in, you set up each "site" as listed in the RR database, as if it was its own single site.

To sum up: "Site" in RR refers to a Uniden zone, not "transmitter tower site." And an "RR site" might be one transmitter or a bunch of transmitters grouped together. But either way, you consider an "RR site" as a single site in the UASD software, regardless of how many transmitter locations, and you will be good to go.
 

Airdorn

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Hey, thanks for that detailed explanation N1CTF!

http://www.radioreference.com/apps/db/?sid=4361

That's the Memphis/Shelby County PS System. It lists 2 different sites. If 1 site is a clone of the other site, then why does one site have more frequencies than the other?

Also, did you mention that ALL those frequencies could just be combined into 1 big frequency list under 1 site under a single System? I have the BCD996T.

Right now I have the 996T setup like the RR database. Namely, two sites under a single system. It seems to work, but I noticed that even though site 1 is pretty much for Memphis Police Department and the Corrections TG's, that's not always true. I'll sometimes see MPD spilling into site 2. There's some other cross-overs as well.

So I think I'll just leave it as I have it now... each site has its own quick key, but both sites exist under a single System.

Thanks again!
 

matthewtomek

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Airdorn said:
Hey, thanks for that detailed explanation N1CTF!

http://www.radioreference.com/apps/db/?sid=4361

That's the Memphis/Shelby County PS System. It lists 2 different sites. If 1 site is a clone of the other site, then why does one site have more frequencies than the other?

Also, did you mention that ALL those frequencies could just be combined into 1 big frequency list under 1 site under a single System? I have the BCD996T.

Right now I have the 996T setup like the RR database. Namely, two sites under a single system. It seems to work, but I noticed that even though site 1 is pretty much for Memphis Police Department and the Corrections TG's, that's not always true. I'll sometimes see MPD spilling into site 2. There's some other cross-overs as well.

So I think I'll just leave it as I have it now... each site has its own quick key, but both sites exist under a single System.

Thanks again!
These are actually 2 different "systems" built into one. All public safety is on Site 1. Everyone else is on Site 2. If Site 1 frequencies become full, the radios will automatically swith to Site 2 to talk via the Smartzone.
 
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