Help with understanding simulcast "site" structure

hanlonmi06

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I was looking around in the MPSCS database and found myself looking at FCC database information for the Washtenaw County simulcast site. I was looking at the licenses and frequencies and basically got completely confused. I see three call signs with a total of 8 street addresses for a total of 7 sites comprising the system and not all exactly the same frequencies listed for each given call sign. I'm not trying to solve a problem with anything scanning wise, just trying to understand what makes that system tick. I had thought I had a basic understanding of a simulcast system, multiple towers broadcasting on one FR frequency but is it still that simple in practice despite there seeming to be more to it as observed above?
 

kayn1n32008

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A Simulcast system has multiple sites, all utilizing the same frequencies. The idea is to saturate the intended coverage area, where through timing and phase control, all transmissions arrive within a very controlled time(called ‘delay spread’). With in the confines of the delay spread, it almost appears to the radio, it is receiving a singular signal. C4FM is unforgiving, and has very little tolerance to signals arriving at different times, this is why there are three or 4 variants of PSK used(LSM ect.) The variants of PSK allow for a much wider delay spread than C4FM. Old school scanners do not properly receive The PSK Variants due to Using a discriminator tap, verses an I&Q receiver like in the SDS scanner series. This causes ‘Simulcast Distortion(it’s a scanner issue, not a simulcast issue)
 

hanlonmi06

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I should clarify, this wasn't intended to be a post about why I cant receive a simulcast system well.

For argument sake, what I imagined a simulcast system looking like from a functional standpoint was for example, 10 tower sites and each tower having all the same 10 RF frequencies. Those ten towers being scattered about for a large geographic coverage.

What it looks like when poking around and looking at FCC data and so forth doesn't appear to match that idealized system, so I was wondering why that was? What did they do in setting up Washtenaws system? Are some tower sites operating as multi cast and simulcast, linked with other MPSCS towers? its basically all just curiosity sake.
 

fredva

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The OP didn't ask for why simulcast problems were difficult to receive, and it's important to use the correct terminology when trying to explain something. A simulcast SITE has multiple transmitters utilizing the same frequencies. For simulcast, the term site is not the same thing as a single transmitter.

I see some variations in the frequency list for that site but I'd need more time to study it in depth and do a more thorough comparison of the towers and frequencies between the three licenses.
 

hanlonmi06

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whoa.........thank you.

scanmanmi, does that map have a legend available? I find it ironic that washtenaw counties break out looks like the most spaghetti
iMONITOR, that will keep me busy for a while

thank you both!
 
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