Tracking LTR systems can be daunting. Here are a few tips from the experts!

Robert H. Eisner asked:

>I've been trying to program my 780xlt with an LTR system here in the San Francisco Bay area and have been unable to get it to work. The system that I'm currently trying to Track is using the same Area and Home Repeater on all frequencies. If this LTR system is not very busy, then all conversations stay on the Home Channel of 463.4250. When the system starts to get busy one of users will generally hop to 461.1500 or 461.4750. However, the Area and Home repeater are always 0 & 07 for all frequencies.

>Can the 780xlt track this type of LTR system? I had to enter the Home Channel of this system into slot number 7 to get the 780 to stop on it in search mode. What am I suppose to do with all of the other frequencies? I can't enter all of them into slot 7.

Carl Guse answered:

Yes, the 780 can track LTR systems. For it to track properly, you must determine the repeater numbers of the other channels. Obviously 463.425 is repeater #7. The seven other freqs that you have identified as being part of this trunking system also have repeater numbers. Once you have determined these repeater numbers, you must program these frequencies in the channel that corresponds the repeater number (repeater 1 in channel 1, etc). Even with LTR decoding software such as CSI's, it can be difficult to determine repeater numbering on some systems. You can start out by programming 461.150 into channels 1 thru 6 and 8 thru 20. When you see traffic being trunked to that freq, note what channel it is, that will be the repeater number. Then do the same with 461.475, and so on with the other freqs. The repeater numbers will always be between 1 and 20.

And Todd Hartzell also answered:

My experiences with the 780xlt is that its LTR function is similar to EDACS programming. You must program LTR in the logical-channel order of the system. If you do not, the 780xlt will ignore talkgroups that are not on their correct channel number. I've heard this problem several times on Trunkcom. Owners of the Pro-92 expecting the 780xlt to perform and function exactly like their 92. It doesn't (The Pro-92 isn't a Uniden product). The 780xlt actually expects the repeaters of an LTR system to be programmed in the correct Logical-Numbered Order. The Pro-92 did not. The actual 'Trunk System' radios also require the repeaters to be programmed in the correct logical order. So in that respect, the 780xlt functions more like the actual Trunk system radios ; the Pro-92 does not.

With St Louis Missouri LTR, I have found numerous systems that place all of the repeaters well above slot-5 (LCN-5). Or even slot-10 (LCN-10). I have also found some systems were several repeaters work in the same slot number (LCN-number). It will take some tinkering, but you should be able to find all of the unknown repeater-slots (thru trial-and-error). It might take sometime, depending on how busy your local LTR system(s) are.

So why do multiple repeaters work in the same slots as others. I believe it has to do with the 'Home Channel' function. Do matter what repeater a talkgroup pops up on, its unique Talkgroup number is going to include its Home Channel-Slot ; as apart of its unique ID. And the radio seems to except that it is on its assigned repeater slot, even if it is not. Say for example: (I will use a St Louis LTR system as an example)

464.275R -- 0-09-066 --> Barnes Hospital Security

If it were to popup on another repeater, and if the other repeater were programmed in slot-9, the 780xlt should except it. Note, Barnes Hospital Security's home Channel is Repeater-9 (Slot-9). That's it. This is the only repeater that I have found them on.

This can be quite a confusing problem, when trying to figure out LTR's Logical Channel Order. I wish ya luck on cracking the logical order.

Don't be surprised to find some of the Logical Channel numbers of some systems well up in the Teens or maybe 20+ range. Its very possible.

Dave Stark responds as well:

This kind of thing only seems to happen on UHF LTR systems in my area. The 800 MHz systems are better behaved. The user's home repeater is always the same, and their ID always reflects that.

When a user whose ID is 0 03 224 goes to repeater number 05, their ID is still 0 03 224. This reflects the fact that this user's "home" repeater is 03.

When all users on a system are "homed" on the same repeater, each repeater's number is different but impossible to determine from user IDs. You will never see another repeater number, so there is no direct way to determine the numbering system. However, there is an indirect method. You just can't do it with the BC-780 in trunking mode.

What you need to do is to watch the users as they rotate through the trunked repeaters. Channel number order will be the same as the order in which they use the repeaters (in other words, they rotate "forward"). This does not mean that the first repeater used is channel 1, however. When the system is quiet, the first repeater used will always be the "home" repeater, so you will have that number right away. The next one used might be a higher number, or it might be lower, depending on what number you're starting with and how many repeaters are in the system.

So, in a system where everyone is "homed" on channel 05, you might end up with:

05-??-??-??-??

Another phenomenon that seems to be common to UHF LTR systems is the so-called "Rule of 4" for repeater numbering. Repeaters are numbered in increments of four rather than the customary increment of one. In the above sequence, I would subtract four from the lowest known channel number. If it is 01 or higher, then that repeater number is possible. In the above example, I would have:

05-??-??-??-01

Applying the Rule to the rest of the repeaters, I deduce:

05-09-13-17-01

To verify, just punch the repeater frequencies into the BC-780 according to the above numbering and see if it tracks. If it does not, then either the home channel was misidentified, one or more repeaters are missing, or the Rule of 4 is not in effect for this system. Keep experimenting until it works.