Got a Question

[teufler]

All of use who have a scanner mobile have listened to the police and if they were running a speed trap, we had a rough idea of where they were at. Prior to Trunking, you could monitor the direct frequency or if on a repeater you could mintor the input then looking at the signal strength indication, you through experience knew how far away the speed trap was. So now with a trunking system that has been established, how do we determine where they are at? We are not breaking any ham rules, we are not using a radio to break any laws, but can you monitor an input and how do you determine what input they are using when the system being used has 12 or more frequencies? I have a 396xt, .

 

[nd5y]

Motorola and P25 trunked systems send the input frequency on the control channel when the voice channel is assigned but Unitrunker ignores it. I don't know if there is any other control channel decoding software that shows input frequencies.

Some bands have standard offsets so it is easy to find the inputs.
If the trunked system is in the 935-940 MHz range the inputs are 39 MHz lower.
If the trunked system is in the 851-869 MHz range the inputs are 45 MHz lower.
If the trunked system is in the 746-776 MHz range the inputs are 30 MHz higher.
If the trunked system is in the 470-512 MHz range the inputs are 3 MHz higher.
If the trunked system is in the 451-455 or 460-465 MHz range the inputs are 5 MHz higher.
If the trunked system is in the 406.1-411 MHz range the inputs are supposed be 9 MHz higher unless it is a legacy system that doesn't conform to the current band plan.
If the trunked system is in the 380-390 MHz range the inputs are 10 MHz higher.
If the trunked system is VHF there is no standard offset. You will have to search FCC license data to find the inputs and figure out which inputs go with which outputs.
Newer federal government or state systems using federal frequencies (like MOSWIN) should have outputs in the 169.5-173.2 and 173.4-174 MHz ranges and inputs in the 162-166.5 MHz range unless it is a legacy system that doesn't conform to the current band plan. There is no standard offset.

 

[teufler]

thanks

well I will have to work on it. Sometimes the old repeater system were better for scanners than the new trunking repeaters.

 

[JoeyC]

You listen to all the inputs and take your chances.

 

[krokus]

Use SDR software, and set it up tune to the input instead of the output. It will take a little work.

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[wtp]

nyself

i have a system labeled "input" for my county system.
and by the quality of the signal i can guess quit well how far away they are.
usually within a mile i can hear them and guess the rest.
one night i thought they were right on top of me and they were across the street !
it also works great for "on the scene" stuff but then i can't hear dispatch.

ok i meant myself...

 

[teufler]

I guess inputs would not be the control channels so leave them all out . I can do that much. Tes listening and looking at the s meters, you can guesstimATE the distance to the target.

 

[wtp]

only one

one channel for control here, and ours get changed every 24 hours or sooner. so to me its not worth the effort to take one out.

 

[Voyager]

As has been mentioned, scan the input frequencies conventionally. That will give you the exact same intel that you had before.

 

[slicerwizard]

I guess inputs would not be the control channels so leave them all out . I can do that much. Tes listening and looking at the s meters, you can guesstimATE the distance to the target.

Why would you need to remove the control channel input frequencies?

one channel for control here, and ours get changed every 24 hours or sooner. so to me its not worth the effort to take one out.

Or you could just ignore that bad advice...

 

[teufler]

WELL i CREATED A SYSTEM, WITH THE SITES LEAVING OUT THE "COLORED" CONTROL CHANNELS, per RR database. Then I had to switch to a outside antenna to be able to hear input traffic if in the neighborhood. So far nothing has been heard. I was listen to the state troopers and a state airplane. Just curiousa how far away they are, though sometimes I ear the pl;ane as I live close to the interstate and a favorite "shooting" site is just west of here about 4 miles. Speed limit is 60 anfd today there were some 86 andf 89 speeds, one 90+ as he drove through the blocks then he sped up as the chase car entered the highway. Couple of nights ago, had a car get to 130+ and the troop gave up the hunt on him. About one a month, some crotch rocket is going 150 plus, and rarely are they stopped.

 

[wtp]

i would put them in

as long as they could be used for voice they should be in.
i got a chance tonight at dinner to use the inputs. the restaurant is in a horrible reception spot and near a state tower which has channels all around my counties output. and the only thing i got to hear was an ambulance checking in. even with the radio on the table it is a bad reception but got to hear something even with it in my pocket.

 

[slicerwizard]

Scanning trunk inputs (all of them) is a great way to track down things like undercover operations. They rarely announce their location when they're not mobile. If you can hear them, you're close. If you can remove your antenna and still hear them, you're very close. When the warrant arrives and they kick in the front door at 0445 (their favorite time around here), you're set up to get vids for the morning news.

 

[puzzleriddle]

Inputs re -45mhz on 800 not sure about other bands

 

[teufler]

This is worth knowing because without the knowledge of a mobile near by, we are "flying " blind. So to speak. While trunking allows you to hear both sides of the conversation, it makes it hard to figure out where they are at. When the airplane is up, if you don't hear a response, they were usually out of the area. Then a response, you were getting close. The airplane used to say, such and such at mile post XX. Now its just, the next car on your left, a speed and thats the correct one and a time. If you heard a mobile, usually scratchy but if they started to clear up, they were in front probably and you best be alert. .