BCD325P2: Losing signal on trunked systems?

IStebleton

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I am currently scanning a couple P25 systems, and about 4 sites. For whatever reason, one or more sites randomly lose signal, then come back. My scanner is not moving, so I am wondering what the cause of that is.
 
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what the cause of that is.
Any chance you have a priority mode turned on?

Weather or Close Call or other Priority modes?

Check the display carefully when the signal drops out.

If not, chances are you are too far away from the transmitters.
 

IStebleton

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Any chance you have a priority mode turned on?

Weather or Close Call or other Priority modes?

Check the display carefully when the signal drops out.

If not, chances are you are too far away from the transmitters.
I'm 2.7 miles from the one site that is giving me problems. I don't have any priority or weather scan happening.
 

ofd8001

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Are you looking at the signal strength meter and seeing the signal drop then come back? If so, this is normal behavior - it is part of the scanner "cleaning house" before it does its thing again. Nothing to be concerned about.

If it cuts in and out during a voice transmission and there are no priority things going on as described above, I concur with Simulcast Distortion.
 

hiegtx

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I am currently scanning a couple P25 systems, and about 4 sites. For whatever reason, one or more sites randomly lose signal, then come back. My scanner is not moving, so I am wondering what the cause of that is.
I'm 2.7 miles from the one site that is giving me problems. I don't have any priority or weather scan happening.
Is this the system you are trying to monitor?
And are you in Butler County?

The Butler County site is most definitely simulcast. Look at this map:
88158

On the site details page it is listed as a "six site simulcast system"

But as the map above shows, it's more than that. I took a look at the three listed licenses (near the upper right corner of the map), and it appears that there are a dozen sites in use. Simulcast issues include causing transmissions to break up, sound garbled, or show full signal strength in the scanner's display, even though no audio is being heard. While the 325P2 is a good scanner for many areas, it is not where simulcast is involved. Simulcast is extremely location specific, even to the point that your reception may improve (or get worse) with as little as moving the scanner a few feet in one direction or another at your house.

Read the Simulcast Distortion wiki page that Doc linked above. In some cases, you might have better results with less of an antenna, or no antenna at all other than maybe a paper clip. One tactic that works in some cases is to use a directional antenna, such as a yagi, and aim it at one specific site location.

You say that you are 2.7 miles from one site location. Try getting closer, like a quarter mile or less. If you then start hearing more traffic, and more clearly, then simulcast is your problem. The problem that the scanner is dealing with is that all these sites are transmitting the same radio traffic, at the same time, on the assigned frequencies. Signals from a dozen sites, all the same frequency & talkgroup, will arrive at your scanner at different times, due to their distance from you. While the time differential is extremely small, it's still enough that the scanner cannot successfully decode the radio traffic. If you get very close to one site, as suggested above, then that very strong signal from the one location may be enough to override the signals from other sites that are farther away.
 

IStebleton

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Are you looking at the signal strength meter and seeing the signal drop then come back? If so, this is normal behavior - it is part of the scanner "cleaning house" before it does its thing again. Nothing to be concerned about.

If it cuts in and out during a voice transmission and there are no priority things going on as described above, I concur with Simulcast Distortion.
It's just that the signal bars vary every couple minutes. I did not realize that that was normal. Thanks for your help
 

hiegtx

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I am scanning the PA STARNet P25 System, specifically the Allegheny Region Simulcast on the WEST03 tower
Good deal. That specific site is not simulcast, so as already noted, you're likely seeing the house cleaning.
 

gmclam

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Could it be because of a strong nearby cell tower? When the cell signal is active, reception from the intended site goes away.
 

GTR8000

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Good deal. That specific site is not simulcast, so as already noted, you're likely seeing the house cleaning.
The word simulcast is literally in the name of the site. WEST03 is one of five subsites making up the Allegheny Region Simulcast cell.
 

n1chu

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There’s some confusion about the term simulcast. People submit data to RR and call it what THEY think it is. It could very well be simulcast but not always. There’s another term (which eludes me) that acts much like simulcast but isn’t. Hopefully, someone here will have the answer to that which eludes me. I’m not saying you are wrong, merely pointing out the data submitted to RR comes from us mostly. There are RR administrators that are supposed to vet all that is submitted, (and input their own research backed entries) but that’s not always the case.
 

kruser

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There’s another term (which eludes me) that acts much like simulcast but isn’t. Hopefully, someone here will have the answer to that which eludes me.
Multicast?

A counties analog VHF system here had three transmit sites that all transmitted at the same time on the same frequency much like today's simulcast systems but it was a technology called multicast. It also had problems similar to LSM but being an analog system, it was much more bearable to the scanner listener.
I lived a ways away and their signal sounded fine for me but others near the county center complained a lot.

I think there may have been another simulcast list system also by multicast it the one I recall.
 

kruser

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Yes, multicast. Thanks!
There was another called Anycast as well. Or... I could be confusing multicast and anycast! I's been a while since it was on the air plus my brain is foggy from those days.

Either way, they attempted to keep the signals synchronized with each other with some type of clock. I think it worked pretty well for the users but for a scanner listener who was not within the counties intended coverage area, that's when the problems were seen. A lot of signal cancellation etc.
And like today's simulcast systems, it you lived for enough away from the county, reception was normal as you really only captured a decent signal from one tower.
 

GTR8000

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There’s some confusion about the term simulcast.
I'm not confused at all, and I'm fully aware of what "simulcast" means, believe me.

The commonly accepted definitions in the radio world are as follows:

Simulcast: multiple transmitters/sites all broadcasting the same transmissions on the same frequency/frequencies simultaneously

Multicast: multiple transmitters/sites broadcasting the same transmissions on a different frequency/frequencies

A simulcast trunked cell is a single virtual "site" comprised of multiple subsites. A subsite being defined as one of two or more physical locations, all of which together form the simulcast cell. While a simulcast cell appears as a single site to receivers (e.g. Site 1), there is obviously more to it than that. Conventional channels can also be simulcast in a similar fashion, where you have a few transmitters covering a wider area than a single transmitter could, all putting out the same signal simultaneously, e.g. a Fire/EMS paging channel that has multiple sites covering an entire county. And yes, signal timing is critical, and thus modern simulcasts (trunked or conventional) are kept in sync using a GPS signal.

An example of a multicast might be a signal that is carried on both UHF and 800 MHz at the same time so that agencies operating within each band can receive the same broadcasts. There are other examples that get a bit too much into the weeds, but that's a pretty common example. Technically a trunked system that operates across multiple bands could be said to be "multicasting" the talkgroups across those bands.

In keeping with the topic of this thread, the PA STARNet P25 system has sites operating in the VHF, UHF, and 700/800 bands, comprised of primarily standalone (non-simulcast) sites, but also three simulcast cells in the mix. The Allegheny Region Simulcast cell happens to be one of those three, and happens to also be what the OP is trying to receive.

Class dismissed. ;)
 

kruser

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Simulcast: multiple transmitters/sites all broadcasting the same transmissions on the same frequency/frequencies simultaneously
Way back in the old days, FM/AM Broadcast radio used to use the term Simulcast for "simultaneous broadcast". Simulcast is what they called it on the air. The same signal was sent over their AM and FM stations at the same time using different frequencies of course.
We had a station here that was very proud about being able to simulcast their shows on their AM and FM stations.
I could be wrong on this part but I think the FCC rules back then made them break the simulcast and announce only the correct call for the given transmitter when it was time to announce the call.

The system I was thinking of earlier was called Synchrocast.
It's mentioned in the Wiki for Jefferson County, MO: Jefferson County (MO) - The RadioReference Wiki which is the user I remembered.
 
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