Very Confused

mike36507 · #1 (**permalink**) 09-16-2009, 09:58 PM

I have recently began mapping some LTR systems in my area. On at least 2 different systems all of the frequencies hit on the same LCN and some on the same exact TGID. This does not make sense to me because as far as I know is each frequency has its own LCN because I can not reuse the same LCN twice ina system when programming my BC246T. Is it possible that one callsign that has 3 frequencies has 3 different system that use the same exact TGID on each??? That sounds insane, but I think that is what I am seeing. Here is one of the systems I have been mapping (attempting).
ULS License - Industrial/Business Pool, Trunked License - WPXG444 - CSA Equipment Company - Frequencies Summary

n4yek · #2 (**permalink**) 09-17-2009, 12:57 PM

Quote:

Originally Posted by mike36507

Is it possible that one callsign that has 3 frequencies has 3 different system that use the same exact TGID on each??? That sounds insane, but I think that is what I am seeing.

If I follow you on this, an LTR system in my area has something like you describe.
The local Fire department utilize what we refer to as a 'wide area' talkgroup. In other words, they utilize the same talkgroup on 3 different sites simultaneously. This is to insure the communications are heard by all users and all they do is switch channels on their radios to the closest tower site when they transmit and then the tower transmits the audio on the other sites as well.

As for your LCN problem, it can be a pain to figure out LTR systems. Just hang in there and keep trying.

aharry · #3 (**permalink**) 09-17-2009, 03:12 PM

Mike,
Read this article in the WIKI and it should answer your questions... it's smoke and mirrors when mapping LTR systems!

Mapping an LTR System - The RadioReference Wiki

mike36507 · #4 (**permalink**) 09-17-2009, 04:47 PM

Yeah I have read that before and I have mapped other LTR systems successfully, but these that I am doing now are giving me the same exact TGIDs on every frequency within the system. Also today I heard one half of a conversation on one TGID and the second half on another TGID. I think my radio is on the fritz or something....lol. So far I have seen this on 4 different systems, all of them doing the same thing. It is really weird. I'm not even for sure whether or not they are LTR Standard, but it is giving me those type of TGIDs that are found in LTR.

mike36507 · #5 (**permalink**) 09-17-2009, 04:51 PM

That may be how these systems are here too Danny. That does make sense, but can an LTR system use on 1 frequency?

milf · #6 (**permalink**) 09-17-2009, 05:47 PM

You can have single freg ltr sites. I have heard of an system liced for three freqs,.. but only ONE was actually trunking, the other two were conventional. As to having multiple freqs at one site, with each freq iding as an separate system, I guess thats what your describing, is an interesting puzzle.... Good luck, as LTR's are both fun and annoying to map...

mike36507 · #7 (**permalink**) 09-17-2009, 06:55 PM

I do think all of these frequencies are trunked. In conventional I hear the "keying up" sounds on all of them at about 10 seconds apart. Thats what leads me to believe its LTR. On the other hand, do any other trunking systems have the same keying up sounds?

n4yek · #8 (**permalink**) 09-18-2009, 10:53 AM

Quote:

Originally Posted by mike36507

That may be how these systems are here too Danny. That does make sense, but can an LTR system use on 1 frequency?

I know this is wrong to state it like this, but think of the LTR ID as a 'pl tone' to access the repeater. Unless the repeater receives an LTR ID, it won't key up. They might just be using assigned freqs for each user, ( maintenance on one freq, ops on another, etc...), and using the same LTR ID to access the repeaters.

milf · #9 (**permalink**) 09-19-2009, 01:59 AM

If its actually having data bursts at the 10-12 second interval its LTR ... If you had an PRO-97 I know they show the HR number and that helps for mapping.... Unless its VHF LTR then the 97 is out... On the PRO-92 and that generation you can at least get the tg's... as no proper LCN is needed... Otherwise you have to use the two methods in the wiki.. an pita but worth it to get the right configuration figured out.... Its work to do but I find it fun... Almost as fun as figuring out complete multisite Motorola TRS's and P-25 stuff.... The only system I hated mapping was an EDACS back when the first gen of EDACS capable scanners came out.... If you can set up a data slicer and run Universal Trunker, or Trunk88 on it it may help you get it nailed...

slicerwizard · #10 (**permalink**) 09-19-2009, 05:08 AM

Quote:

Originally Posted by milf

If you can set up a data slicer and run Universal Trunker, or Trunk88 on it it may help you get it nailed...

On an LTR system? I don't think so. Try LTR Analyzer and an audio cable.

mike36507 · #11 (**permalink**) 09-19-2009, 01:26 PM

with LTR Analyzer, do you have to have a discriminator tap or does the audio cable just plug into the jack. Because I know nothing about installing a tap and wouldn't want to screw my radio up.

slicerwizard · #12 (**permalink**) 09-19-2009, 06:38 PM

Yes, you need a tap. The filtered audio from the headphone/speaker jack distorts the low speed data to the point where it's useless. Many scannerheads get their hands on an ancient non-trunking scanner and tap it.

milf · #13 (**permalink**) 09-19-2009, 10:09 PM

Or get one of the PRO-92's or 2067's takes about ten minutes tops to tap.. I even have pics of tap points for you if needed.... These were like, designed for tapping lol.

mike36507 · #14 (**permalink**) 09-20-2009, 09:35 PM

Quote:

Originally Posted by slicerwizard

Yes, you need a tap. The filtered audio from the headphone/speaker jack distorts the low speed data to the point where it's useless. Many scannerheads get their hands on an ancient non-trunking scanner and tap it.

I have a BC895XLT that I really never use, it doesn't track LTR but would I be able to tap it and use LTR Analyzer?

mike36507 · #15 (**permalink**) 09-20-2009, 09:40 PM

Quote:

Originally Posted by milf

Or get one of the PRO-92's or 2067's takes about ten minutes tops to tap.. I even have pics of tap points for you if needed.... These were like, designed for tapping lol.

Do the GRE radios have this same function, and also do the newer RS radios like the Pro-163 have the function?

aharry · #16 (**permalink**) 09-20-2009, 09:51 PM

All FM radios have baseband audio.. it's just a matter of locating the signal and routing it to the outside of the radio via a jack or cable. Some radios are easier than others in that a lot of RS scanners have "test points" located on or very near the chip that outputs the signal so you don't have to solder directly on the chip. Soldering on the chip pins is not a probem if you have the right equipment and experience, but too much heat on the IC could fry it.

milf · #17 (**permalink**) 09-21-2009, 12:28 AM

The older GRE made for RS scanner have the easiest to find/use discriminator pins etc... The Uniden made for RS seem to be a lot more complex to tap..... I have no idea on the newer GRE for RS, and actual GRE scanners tapping..... Take the RS PRO-2052 for example... That one requires a lot of patience and from looking at the pics of what is needed to do a proper tap o that thing.... A good work center lol... Where as with the 92/2067, open it,.. solder wire to two simple to find hard to hurt spots and your good to go...