St. Louis Fq. Problem

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mikie333

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I have having issue with a certain fq in the STL area...the Central County Fire Alarm: 154.2200...it used to work fine untill now, is it my scanner, or does anyone else notice this problem? It sounds completly muffed! I know theres not a problem with them, cause when i'm at the firehouse, their calls come in clear...

thanks!
 

Starcom21

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They could have simulcast towers (multiple towers on the same frequency that are not alligned up perfectly) and what you actually hearing is like a 1/4 second delay in the second tower or something.

Having the same problem with St. Clair County in IL on 154.19.... completely muffled.
 

Starcom21

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Exactly what it sounds like to me..... not horrible here but can here it. I'm probably far enough away from all the transmitters.

I can hear it more on the the paging tones than on the voice.
 

N9PBD

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It sounds like two transmitters on the same frequency, one not strong enough to capture the receiver, but still some out-of-phase noise on the signal. I have a strong signal here in O'Fallon, IL, with a very small amount of occasional flutter on the signal.
 

mikie333

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well does this only affect the scanners, cause like i said-when im at the firehouse, it comes in as clear as ever...
 

Starcom21

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Just to clarify, I'm sure your talking about base stations only that sound like this, then maybe you have one of the base stations located near the department and that one over powers the other transmitter and you just dont' hear it at all.

OR maybe the one transmitter is at your station and you always only here the other transmitter.... not sure on the set up of the system.

Which agency is this?

Is this North Central or Central County dispatch? Which PL tone is it?
Which "station" do you here it OK at? Where is it located?

Terry
 

jas0nr7272

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A commercial radio will receive much better than any scanner. That is why you get good reception in the fire house.
 

shelleys1

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jas0nr7272 said:
A commercial radio will receive much better than any scanner. That is why you get good reception in the fire house.

That and he's specifically "toned-out" when Monarch (or any of the other districts dispatched by CCE 911) receives the call. The dispatcher clicks certain buttons on his/her screen, distinguishing which pieces of equipment, in which houses, are going to be dispatched on the call. Then only those specific locations are sent the tone and the signal, along with the voice dispatch, directed that way from Central County's 200' tower and a sheet is printed out at the station as well.

The time in question, when you were hearing some "muffled" and distorted dispatches, I know Central County was both having some work done and, I believe, upgrading some things on their system. That could have been part of the problem. Also, make sure the PL tones are entered correctly.

Shelley
 
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scanman1958

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Shelly, I have also heard what I would describe as staticky transmissions from CCE911. It is similar to when you are talking on a land line phone and you have a loose connection on your handset. Any idea what that might be?

Jeff
 

902

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154.2200 MHz is a SYNCHRONOUS SIMULCAST system. What all this means is that multiple base stations, each at a different location, transmit the same information at the same time. The result is a net improvement in coverage. But there is a tradeoff. What is frequently heard is phase distortion as a result of multiple overlaps or from multipath (reflections) from various ground formations and construction. There can be deep and rapid fades as the signals cancel out (remember addition and subtraction of sinusoidal waveforms in geometry?). If one of the sites goes out of lock, you can also hear heterodyne, which is generally more destructive.

Synchronous simulcast is less noticeable in a digital domain where machines, not the human ear, contend with the multipath and phasing errors. In analog it's a tradeoff to "better" coverage.

Note that these systems are ENGINEERED to blanket a specific area with signal, in this case the Central County E9-1-1 catchment area... there is no compelling reason to cover a greater area and to do so effects the economy of the system. The overlaps within this specified area can be adjusted within reason, the fewer the better. If you are on the periphery or outside the intended area of coverage, the overlaps would not be optimized and reception would be poor quality, even though theoretical signal levels should be higher.
 
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jayres

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And to think, I can hear them coming in loud and clear down here in Lebanon, MO... You all just need to move farther away... lol
 

902

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jayres said:
And to think, I can hear them coming in loud and clear down here in Lebanon, MO... You all just need to move farther away... lol
Good signal 115 miles away from the area they intend to cover? Their ERP may need to be adjusted down somewhat.
 

mikie333

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well, its official, i'm an idiot! i fixed my problem about a week or so after i started this thread...

i feel imbaressed to say what my problem was, but here goes...

i was listening to that fq. in AM, as opposed to FM...wow

well, thanks for all the great info...sorry to waste your time!
 

902

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While it may not be the best way to listen to what you wanted to, using a different demodulator could be helpful in identifying system problems you couldn't hear in FM. You just discovered it by mistake.
 

mikie333

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902 said:
While it may not be the best way to listen to what you wanted to, using a different demodulator could be helpful in identifying system problems you couldn't hear in FM. You just discovered it by mistake.

remeber, 902, i'm not as advanced as y'all...Demodulator?

but thanks!
 

902

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mikie333 said:
remeber, 902, i'm not as advanced as y'all...Demodulator?

but thanks!

Everybody has to start somewhere.

The demodulator is the circuit that recovers information from a radio carrier. Better receivers may have different circuits you can program or switch so that you can monitor different types of signals.

Here's the wikipedia definition:
http://en.wikipedia.org/wiki/Demodulator
 
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