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SCPD

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Feb 24, 2001
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65,126
Location
Virginia
Hello, I'm from Michigan and have a question about your highway patrol.

I have been reading different people say that you can't hear a THP car unless you are right on top of it.
So this may seem to be a silly question, but how is dispatch hearing the car?
There has to be some frequency, whatever it may be, where the cars are loud and clear for miles and miles.
 

W4EMS

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Premium Subscriber
Joined
Dec 19, 2002
Messages
585
Location
Middle Tennessee
They are on low band and run ~100 watts but the terrain attenuates the signal.
They use remote receivers for the base to hear the mobiles but for scanning purposes you do need to be within a mile or so.

They also use mobile data terminals now for a lot of traffic. So not only are they hard to hear they are talking less. Eventually they will move to the new TN trunking system but that is a few years off.

Does help some in that if you hear a mobile you know they are close and to watch your speed :)
 

n4yek

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Joined
Apr 20, 2004
Messages
2,479
Location
Newport, Tennessee
It all depends on where in the state you are as to how you will monitor them. In the eastern part of the state, they use 70 MHz links between the dispatcher and the trooper. To monitor both sides of the conversation you will have to enter the 40 MHz freq and the 70 MHz freq to hear them both.
In other areas you can hear them on UHF freqs, some are on area trunk systems that will eventually become part of the state-wide system.

It all depends on where you are located as to how you monitor them.
 

jimg

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Joined
Oct 8, 2003
Messages
812
Location
So. Middle TN
Hello, I'm from Michigan and have a question about your highway patrol.

I have been reading different people say that you can't hear a THP car unless you are right on top of it.
So this may seem to be a silly question, but how is dispatch hearing the car?
There has to be some frequency, whatever it may be, where the cars are loud and clear for miles and miles.
THP uses relays to hear the mobiles talking back to the post. Some are in the mid-band (70 mhz range) and UHF (450 mhz range), as shown in the Tennessee database. They also use microwave relays, which are not listed in the database, and which I am told can not be heard on a scanner.
 
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