Understanding Simulcast

[Borgie]

So trying to do a little research and found this on radio reference.com https://www.radioreference.com/apps/db/?sid=3508

Now if you click on one say for instance Minneapolis City center Minneapolis City Center Simulcast Site Details (Allied Radio Matrix for Emergency Response (ARMER))

It shows a red circle on a map. I am assuming that is the coverage area. So when I am building a favorites list do I need to just have that one simulcast in the FL for anything in the metro area to work, or do I still need individual county simulcasts like hennepin or ramsey depending what departments I put in?

On the coverage, does the signal get weaker the further out it is from the center?

Sorry for the questions, just trying to get a better understanding.

 

[Whiskey3JMC]

Hi there:
First of all, what scanner are you using?

It shows a red circle on a map. I am assuming that is the coverage area.

Correct

On the coverage, does the signal get weaker the further out it is from the center?

This depends on several factors: topography, elevation, etc. Generally yes, the signal does get weaker the further out you are from a TX site

 

[wogggieee]

Simulcast in this instance with relation to ARMER means that on that particuar site there are multiple towers broadcasting the same thing. You can see the tower locations if you click on the "Site FCC Licenses" on the page you linke (FCC Callsign WPER943 (MINNESOTA, STATE OF)). Those three towers make up the city center site. If you program in that site you would only hear what is on that site, but you're not going to hear everything in the metro. It is slightly counter-intuitive in that regard. An example of how this works is if you're listening to the Washington County Simulcast site you're going to hear Washington county stuff and some Ramsey County stuff since its neighboring but you're not going to hear Minneapolis or Hennepin County.

These kinds of systems are the bane of a scanner listeners existence. With multiple towers all broadcasting the same thing you have the same signal arriving at slightly different times which makes decoding difficult for the scanner and leads to audio issues.

 

[Borgie]

Hi there:
First of all, what scanner are you using?

Correct


This depends on several factors: topography, elevation, etc. Generally yes, the signal does get weaker the further out you are from a TX site

Uniden SDS100

So there is no way of knowing for sure which tower is broadcasting for instance say St. Anthony since hennepin county has multiple simulcasts? Confusing. I just worry because people say if you put too much simulcasts in your scan, then you ,ight miss something.

 

[johnmoe1]

For some clarity:
simulcast = multiple towers all broadcasting exactly the same thing at exactly the same time on exactly the same frequencies. As far as scanners and radios are concerned, simulcast may as well not exist. It is effectively just a complicated antenna.

I think the word you are looking for is site. Yes, it can be complicated to figure out which site(s) will have the audio you are interested in.

St Anthony Police are dispatched by Ramsey County. I assume they are on the west talkgroup (11520). It would be safe to assume that will be on the Ramsey County site (2-3). It looks like it is almost always also on both the Anoka County site (1-2) and Hennepin East site (2-1).

 

[ofd8001]

With analog signals, the farther away from the transmitter, you will see a noticeable loss of signal, typically more and more static. With digital, such as ARMER, you either have it or you don't. I can receive a digital signal in one place and move 100 feet and it is gone. Nature of the beast.

On simulcast: Back in the old days, a radio transmitter would transmit with lots of power, have a gain type antenna which is mounted real high. That was so there would be adequate in-building coverage. The problem with that is the signal would go a good distance. Great for scanner listening, but it resulted in fewer available frequencies for re-use. These days there is a demand for frequencies, which also contributed to creation of trunked radio systems.

So to achieve the same performance for in-building coverage, the radio engineers came up with a new way, simulcasting. That is where a number of transmitters would be installed to cover a certain area. They would be such that all transmit at the same time on the same frequencies - SIMULtaneously broadCASTing. The transmitter power is lower, antennas are not high gain and not very high. The in-building penetration is the same, with a small coverage footprint.

These systems are designed to cover a certain area, plus a little extra. When I was a kid I could hear Minneapolis PD on VHF pretty far away. Nowadays I'm lucky to hear the Minneapolis NS site on the south side of the MOA.

 

[KA0XR]

With analog signals, the farther away from the transmitter, you will see a noticeable loss of signal, typically more and more static. With digital, such as ARMER, you either have it or you don't. I can receive a digital signal in one place and move 100 feet and it is gone. Nature of the beast.

On simulcast: Back in the old days, a radio transmitter would transmit with lots of power, have a gain type antenna which is mounted real high. That was so there would be adequate in-building coverage. The problem with that is the signal would go a good distance. Great for scanner listening, but it resulted in fewer available frequencies for re-use. These days there is a demand for frequencies, which also contributed to creation of trunked radio systems.

So to achieve the same performance for in-building coverage, the radio engineers came up with a new way, simulcasting. That is where a number of transmitters would be installed to cover a certain area. They would be such that all transmit at the same time on the same frequencies - SIMULtaneously broadCASTing. The transmitter power is lower, antennas are not high gain and not very high. The in-building penetration is the same, with a small coverage footprint.

These systems are designed to cover a certain area, plus a little extra. When I was a kid I could hear Minneapolis PD on VHF pretty far away. Nowadays I'm lucky to hear the Minneapolis NS site on the south side of the MOA.

Nice detailed explanation on this - Thanks!

Roughly how far away would you hear Minneapolis PD when they were on VHF years ago? Did they have one central site like the Foshay Tower to cover the entire city and then some as you described? To my knowledge they weren't on VHF for very long sandwiched between lowband and 460 MHz, but this was all long before I was around.

 

[ofd8001]

I lived in Minneapolis in the 60's as a "young 'un" and listened to MPD on a tunable radio. They were on VHF (High) at least until the mid 70s. I don't recall them being on VHF Low as was the fire department. As such I don't know/remember the footprint of the coverage.

I would imagine that there was only one site as simulcast was not "invented" then or at least widely used. Yet, I'm sure they must have had some backup site just in case the primary failed.

 

[KA0XR]

I recall my dad telling me stories about listening to the Mpls. police at the top of the AM broadcast band decades ago on his car radio. Maybe they went directly from one way receive around 1700 KHz to VHF High band?

Problem with simulcasting is that a relatively cheap scanner like my Pro-106 has a hard time with digital transmissions and often 'motorboats'. With increasing use of encryption I haven't bothered to buy a newer scanner, and mainly only use it when I'm away from the Metro Area.

 

[wogggieee]

I recall my dad telling me stories about listening to the Mpls. police at the top of the AM broadcast band decades ago on his car radio. Maybe they went directly from one way receive around 1700 KHz to VHF High band?

Problem with simulcasting is that a relatively cheap scanner like my Pro-106 has a hard time with digital transmissions and often 'motorboats'. With increasing use of encryption I haven't bothered to buy a newer scanner, and mainly only use it when I'm away from the Metro Area.

With software like SDR trunk and an SDR you can monitor it pretty well, simulcast included, for far far less than a new scanner.