help with car to car

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cityfreq

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I noticed that in belton mo the police car to car is the same freq as dispatch the under ch it says f-2, does any one know how this works and am I able to pick it up? it is almost the same with cass county sheriff's but I still only hear dispatch. I have heard belton say switch to 7 when they want car to car. can any one help?
 

vs1988

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What you are describing sounds like a simplex frequency. That means that they transmit and receive on the same frequency. Motorola calls it Talkaround. Basically, units talk to each other on the repeater output frequency. The range is usually limited since most portables put out 5 watts and mobiles about 25 watts. If you're within a couple miles of a transmitting unit you may be able to hear them.
 

n4voxgill

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It is very common in UHF systems to program a channel for car to car using the repeater output frequency. This keeps the signal from going through the repeater and keeps the unit on the frequency so they don't miss any calls from dispatch. The license will read
453.250 FB2, 458.250 MO, 453.250 MO this last entry is the talk around.
 

kb2vxa

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Hi City and all,

There are several ways systems can have thier channel assignments, you'll have to do your homework on any specific one.

The rule of thumb where repeaters are involved is F1 is through the primary repeater, F2 is simplex car to car on the output. Subsequent repeaters follow as F3 is the secondary repeater and F4 the output, so on and so forth. Often there is at least one simplex frequency unrelated to the repeaters.

Using the thumb on the other hand it is the same F1 and the others being through repeaters in surrounding municipalities for interoperability when officers are operating in another jurisdiction. Again there may be one or more unrelated simplex frequencies. This plan was once used in Union County NJ with F6 being common simplex used by detectives and while rounding up escapees from a nearby state prison. It stands to reason they didn't want this stuff broadcast over a wide area.

One important thing to remember is quite often those low power car to car freqencies are unlicensed so you won't find them in the FCC database. It's a perfectly legal way of operating on "secret channels" in an older analog non encrypted system.

One thing I should mention is when more than one band is in use the channel assignments can get scattered all over the place. Just because the channel selector has numbers on it that doesn't say they correspond to the radio assignments or the dispatcher's console. That's a good reason to do your homework, I have heard the radio repair techies wondering which way is up and it can get funny at times.
 

NeFire242

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kb2vxa said:
One important thing to remember is quite often those low power car to car freqencies are unlicensed so you won't find them in the FCC database. It's a perfectly legal way of operating on "secret channels" in an older analog non encrypted system.
I must have missed this law...
 

Joseph11

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It's completly legal for a public safety agency to use a frequency not licensed to them as long as it's low power and doesn't cause interference to another agency.
 

n4voxgill

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Joseph11 said:
It's completly legal for a public safety agency to use a frequency not licensed to them as long as it's low power and doesn't cause interference to another agency.
That is a broad statement. FCC Rule 90.20 states that police may use the frequencies for stakeout, surveilance or raids, maximum power is two watts or less and you must check the frequency to see how they are classifed, if they are not PP then the department must get frequency coordination from the appropriate frequency coordinator. They can not be used for normal operations or for talk around. They must also comply with any state or local laws or rules. Some states and Regional Planning Committees have adopted rules as to what or how frequencies are to be used and by which agency.

Books for defense attorneys point this out and they look for any violations like this to get cases thrown out.
 
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