Take me out to the ball game... / ATT Park

[b52hbuff]

Please find below my notes for the ATT Park LTR system. I used the algorithm described in the LTR Wiki to determine the LCN numbers for frequencies that came active. Basically, you dedicate an entire bank to a single LTR frequency. When a TGID comes active, knock the radio out of TRUNK mode and see which channel you were sitting on. As I determined the LCN, I would lockout the old bank and create a new bank with the next frequency I was trying to determine LCN. Now I have a 780 config with all of the 'missing' LTR frequencies, so if any of them ocme up active for a short while, I should be able to snag the LCN. Note that this system doesn't use the idle bursts, so I don't think a Pro-97 would help much.

For completeness and fairness, I've included the work done by Greg Stramback showing his work in the area. We agree on the LCN numbers and on the common TGIDs.

The notes below include the licensing classification. I'm hoping that some of the licensing experts here can read the codes and let me know whether to expect if the other unidentified/unheard channels could reasonably be expected to be part of the LTR system.

My monitoring was during a two hour period last saturday during the dogers game. As an fyi, the system is monitorable several blocks away from the park.

One other comment I am including the 'talk around' frequencies in Greg's post. I do not wish to 'submit' this information, but I wanted to provide it for discussion. Has anyone ever seen LTR 'talk arounds' use the same frequencies as the LTR system itself?? Seems like a situation ripe for interference. Is this some sort of fail soft configuration?


Original documentation:
Greg Stramback
http://groups.yahoo.com/group/bayscan/message/27334 (error in 19)
http://groups.yahoo.com/group/bayscan/message/27689 (fixed & talkarounds)

License WQAF710
http://www.radioreference.com/modules.php?name=RR&action=fcc&cs=WQAF710

Frequency  LCN         License / Input License
451.3125    3	FB2/MO100
		456.3125 FX1/MO100

451.5125    7	FB2/MO100
		456.5125 FX1/MO100

452.0375    	MO100
		457.0375 FX1/MO100

452.0625   11	FB2
		457.0625 MO100

452.1125	FB2
		457.1125 FX1/MO100

452.1875   15	FB2

452.2875   19	FB2

452.8000	MO100
		457.8000 FX1/MO100

461.5250	MO100
		466.525 FX1

1-03-113
1-07-103 Janitorial/Maintenance
1-11-101
1-15-102 Ushers
1-19-100 Security

Additional notes...from Greg Stramback
Talk arounds:

T/A 1 457.0625 DPL: 025
T/A 2 456.5125 DPL: 026
T/A 3 456.3125 DPL: 031
T/A 4 452.0625 DPL: 025
T/A 5 451.5125 DPL: 026
T/A 6 451.3125 DPL: 031

 

[emt331000]

Neat.

Next time, try programming a custom search range into your 396 with C-Ch Only enabled. It will save you a ton of work in determining the LCN!

 

[b52hbuff]

Neat.

Next time, try programming a custom search range into your 396 with C-Ch Only enabled. It will save you a ton of work in determining the LCN!

Thanks for the tip, but it doesn't work very well in this application.

The problem is you need to program a 'range' that covers all of the frequencies in the LTR system. In an RF ocngested area like SF, you're going to pick up a lot of garbage. So I prefer an approach that focuses the radio to the frequenceis you _know_ are part of the range.

 

[emt331000]

Now it's getting even easier.

Since you _know_ the frequencies that are a part of the system, park the search on those particular frequencies and wait until someone transmits. The ID will display the LCN. And you won't hear anything but trunked transmissions, so your RF congested area won't play a big part.

To each his own, though.

 

[b52hbuff]

Now it's getting even easier.

Since you _know_ the frequencies that are a part of the system, park the search on those particular frequencies and wait until someone transmits. The ID will display the LCN. And you won't hear anything but trunked transmissions, so your RF congested area won't play a big part.

To each his own, though.

The problem here, as I'm sure wayne_h will be quick to point out... Is that if you are holding on a 'non-home' channel, the LTR TGID display that is shown will indicate the home channel and not the 'GOTO' channel.



Here is information in the wiki I mentioned in my first post:
http://wiki.radioreference.com/index.php/Mapping_an_LTR_System

The problem with a small system that grows is that it may only have 3 out of 10 home channels assigned to users in the beginning. Finding those are easy because they are used frequently and consistent HH appear. When home channel is in use, the user will be sent to either another inactive HH, a GOTO, or FREE channel. When that happens, the Talk Group ID (TGID) will show up on the GOTO channel as the HH channel, so the actual channel number is not displayed. For example, if HH 01 is busy, TGID 0-01-001 is sent to HH 09. TGID 0-01-001 will display on HH 09, NOT 0-09-001. To make matters worse, if there are no users assigned to a GOTO channel, you will never find the correct channel number by looking at the TGID's displayed. TGID's should be in the form: A-HH-GGG, where HH is the LCN/Home Repeater, and GGG is the User Group Nbr.

============

So if you use the menthod you describe, you'll find the 'HH' (e.g. home repeaters), but none of the FREE channels...

 

[WayneH]

The problem here, as I'm sure wayne_h will be quick to point out... Is that if you are holding on a 'non-home' channel, the LTR TGID display that is shown will indicate the home channel and not the 'GOTO' channel.

Correct. And you won't even get any audio (or the true repeater id like you said) so you better have your eyes glued to the screen.

For this situation that wouldn't even work since you already know the freq is used within the system.

The PRO-97 is the best thing for LTR. Program the freqs in a bank in any order, make sure Prog-trunk is set for a conventional bank, and then scan. It will stop on the freq and display the LTR ID. Hit MAN and you can verify the true repeater ID. Plus the idle beacon decoder, but that seems to only work 50% of the time for me.

 

[b52hbuff]

The PRO-97 is the best thing for LTR. Program the freqs in a bank in any order, make sure Prog-trunk is set for a conventional bank, and then scan. It will stop on the freq and display the LTR ID. Hit MAN and you can verify the true repeater ID. Plus the idle beacon decoder, but that seems to only work 50% of the time for me.

So let me get this straight. Anytime the Pro-97 receives audio from an LTR system... When you hit 'MAN' it will display the GOTO channel?

If so, sweet. I can't wait for rebanding and watch RS start dumping them...

In the algorithm described in the wiki, you need to waste an entire bank to a single frequency. Then when you get out of trunked mode, you can figure out the LCN order based upon which channel you were on when it stopped.

 

[WayneH]

So let me get this straight. Anytime the Pro-97 receives audio from an LTR system... When you hit 'MAN' it will display the GOTO channel?

Yes, it displays the normal LTR ID and then "R##" to represent the repeater id for the current tuned freq.

If so, sweet. I can't wait for rebanding and watch RS start dumping them...

Other than not being able to trunk Motorola on 851-854, the scanner will function 100%. Rebanding doesn't affect as much as it seems.

In the algorithm described in the wiki, you need to waste an entire bank to a single frequency. Then when you get out of trunked mode, you can figure out the LCN order based upon which channel you were on when it stopped.

When you do not know the repeater ids for a channel you start from a blank bank. You program the frequencies in any order and set them as LT. Do not set anything else. This will allow you to scan multiple unknowns but does not allow you to hold a Group ID nor store Group IDs because you have not setup the trunked parameters yet. Once you do then you basically do use up a bank. What I do is mix multiple systems that do not use the same repeater IDs. Doesn't hurt anything and you won't have duplicate IDs because they have the home repeater in the Group ID making them unique to the bank itself.

 

[emt331000]

The problem here, as I'm sure wayne_h will be quick to point out... Is that if you are holding on a 'non-home' channel, the LTR TGID display that is shown will indicate the home channel and not the 'GOTO' channel.

If you are holding on a HOME channel, the 396 will provide audio. If you are holding on a GOTO channel, the 396 will be silent. I don't understand what the problem is.

 

[b52hbuff]

The 'problem' is that it doesn't give you any clue as to what the LCN is. If you're monitoring a lightly loaded system or a system w/o FREE channels, then this won't effect you. But if you're trying to map out a system, then lack of LCN data is a big setback.

 

[WayneH]

The 'problem' is that it doesn't give you any clue as to what the LCN is. If you're monitoring a lightly loaded system or a system w/o FREE channels, then this won't effect you. But if you're trying to map out a system, then lack of LCN data is a big setback.

Exactly! If you have a five channel system and four people from the same home channel want to make a call you won't hear three of them that have trunked off to a non-home channel.

What I used to do pre-97, was program in a freq in slot 1, listen, and keep moving the frequency to another slot until it tracked properly.

 

[b52hbuff]

What I used to do pre-97, was program in a freq in slot 1, listen, and keep moving the frequency to another slot until it tracked properly.

I waste more space. I repeated each frequency 21 times in each bank that was programmed as LTR. When the frequency becomes active, you can determine what the LCN is.

And just to clarify, I have my 780 programmed in such a way for about 1.5hrs during my monitroing session. So in that time, there was no activity on the FREE channels. Either the system wasn't busy enough to use them, or they are not in use.

My guess is a combination of the two...