close call issue

[mvpulsts]

OK so the local EMA added a couple new channels to the county's p25 system a little while back. They dont use it much but i wanted to get them added to my scanner.

I got one of the guys to help me out a little bit and key up his radio a few times and talk on it while i ran close call search on my 396xt.

ok, so it caught 2 new frequencies and stored them but subsequentially i cant hear anything on them while hes using his radio?

i see that i might need to get the talk group id for the new channels maybe? im not really familiar with how this all works and reading through the user guide, even the 'easier to read" one is confusing.

can anyone give me some direction on how to identify these two new channels and get them working in my scanner?

 

[frazpo]

You do not need to program all the P25 frequencies to listen to the radio traffic on a p25 system. You are in an "analog" mindset. What scanner are you using and what system are you monitoring? If you scan in "ID search" mode than the 396 will stop on all TG's (talkgroups) If you run "ID scan" and you do not have the TG id programmed then it will not be heard. I always scan in "ID search" mode.

 

[n4yek]

As you have noted, Close call will show you the freqs used. It will not show you Talkgroups on a Trunk system.
You only need to program the Control channels into your scanner, the trunk system will announce in the data stream what voice channel it is fixing to utilize and your scanner will follow it to that channel.
Like frazpo stated, run your scanner in ID search mode when looking for new ID's.

 

[mvpulsts]

thanksfor the tip! Ill use id search modenext time imover there and see if i can pick it up. im using a uniden 396xt with the latest firmware

i have a question about the frequency though. If im understanding it right, the control frequencies range from 854.01250 to 857.71250. when iran the close call with is radio, i got 2 freuency hits, 809.31250 and 811.31250.

does that make sense if the county just added the two channels to the system? im talking about Dekalb County Ga by the way. i dont have any issues tuning into anything tats already in the database. These two channels (talkgroups??) were added last year and see very little use s far..

 

[frazpo]

Im not sure about the frequencies that CC grabbed. Someone may pipe in and explain that. So are the TG's you are talking about listed in the database? If you scan in "ID search" mode you wil get the TGID as opposed to the TG name. Separate "frequencies" from "talk groups". The frequencies really have nothing to do with identifying who is talking on a trunked radio system. A computer is deciding what frequencies are being used. So I don't think it is likely that the new "channels" you are talking about are frequencies. Probably just new Talk groups.

 

[SCPD]

The frequencies you found with close call would have been the INPUT frequencies which the radio uses to transmit to the P25 repeater. The new frequencies would be in the range you posted.

As posted above on a P25 system you don't need to know the frequencies, just the control channel.

 

[mvpulsts]

ok so i think im starting to get it. i know the difference between aninput freq and repeater freq in the ham radio world. this would be similar?

why didnt i hear him once i started scanning the 2 freqs i caught during the close call? Because i didnt have ID search on? should i scan those two freqs with id searh on to catch them next time?

or should i just lock out the other groups on the county system and scan it with the id search on?

guess im asking what the best way to identify these new channels will be??

 

[SCPD]

ok so i think im starting to get it. i know the difference between aninput freq and repeater freq in the ham radio world. this would be similar?

Yes it is very much like amateur radio, the handheld and mobile units transmit on a group of frequencies which the P25 repeater listens for an broadcasts on the higher frequencies over a longer distance.

why didnt i hear him once i started scanning the 2 freqs i caught during the close call? Because i didnt have ID search on? should i scan those two freqs with id searh on to catch them next time?

or should i just lock out the other groups on the county system and scan it with the id search on?

guess im asking what the best way to identify these new channels will be??

It really depends on what they are:
If they are new frequencies you don't need to worry as when they are used your scanner will switch to them.

If they are new talk groups then run your scanner in ID search mode and you will find them when they are used.

 

[frazpo]

why didnt i hear him once i started scanning the 2 freqs i caught during the close call? Because i didnt have ID search on? should i scan those two freqs with id searh on to catch them next time?

or should i just lock out the other groups on the county system and scan it with the id search on?

guess im asking what the best way to identify these new channels will be??

You need to program the whole P25 system. Not just scan a couple of input frequencies. Your scanner becomes an extension of the P25 system. It uses the data channel to basically control your scanner and tune it to the appropriate frequencies. You may want to do some reading on digital trunking radio systems. Its a cool process

 

[mvpulsts]

I have the whole system programmed in. gotta love freescan and a subscription here.

the next time i go in, i will scan the whole system in ID search mode and see what i can come up with.

thanks everyone for the info

 

[UPMan]

The reason you didn't hear him on the lower frequencies is that each time he keys up his radio, the system is going to assign a different frequency for his comm. If he keyed up a dozen times, you might have heard him once or twice (depending on the size of the system and how busy it is).