Scanning LTR Systems on the Uniden BC796D

[Schnoor1648]

I have had my Uniden BC796D for some time now, but just recently I have been experimenting with LTR scanning. Does the BC796D do a good job of following LTR traffic? The reason I ask is that I have put a system in and when I let it scan under software control I had some inaccurate talkgroups logged. Is this because the system may also have Passport on it?

 

[pro92b]

That is a limitation of the LTR checksum, not the radio. It is prone to allowing false ID's through occasionally. If there is a hit counter in your log, the bad ID's should only have one or two hits each.

 

[W4UVV]

LTR Scanning using the BC796D

The 796D will do an excellent job of LTR scanning IF you enter the frequencies correctly in their LOGICAL channel programing sequence. This sequence was determined by the installer and often is difficult to ascertain because on low volume traffic systems comms tend to default to a "home" channel and other system channels may have low volume traffic. Additionally one or more LTR frequencies in a logical system may not be active for whatever reason.

I wrote a short article on helping id LTR frequencies recently for Monitoring Times magazine. Any iding process is time consuming. There can be up to 20 channels in an LTR system. First I identify all of the LTR frequencies licensed to the particular LTR system. Then I program the lowest frequency into ALL 20 channels on the selected 796D bank for that system. When a transmission is made, I quickly press/release the "hold" button and visually id the stopped channel on which the audio was heard. I repeat this several times to confirm audio is being received on this frequency. If the audio is on channel 9 then I write down that frequency and channel 9 as the relationship. I then delete the lowest frequency entered and enter the next highest frequency for all 20 channels and repeat the process. Assuming all 5 frequencies are active in a 5 channel system and I id all of them with their channel relationships, I erase the last frequency entered for the 20 channel check and enter the 5 frequencies and their associated channels. That's it. I assume you are using ARC250 software otherwise plan to spend a lot of time manually entering information.

The Radio Shack Pro96 supposedly will automatically configure LTR frequency/channel relationships. The downside is that it is more prone to miss LTR transmissions from what I have read.

As mentioned, the biggest problem in iding LTR channels is little or no activity on one or more LTR systems. Much time is spent awaiting for the comm traffic volume to increase to where other frequencies in the system will activate, if ever. The described process does work for the most part, but it is not perfect and I am not aware of any alternative id process that is faster or more accurate using the 796D.

The best source is to have the installer/maintainer provide you with the frequency/channel relationships. I doubt if many installers would do this if queried.

 

[pro92b]

First I identify all of the LTR frequencies licensed to the particular LTR system.

How do you do that? Around here there are many systems that have a different call sign for each repeater. Each tower has many transmitters and I haven't been able to gain much from FCC records. In some cases the records do not reflect actual usage probably because the comm company didn't send in an update.

The Radio Shack Pro96 supposedly will automatically configure LTR frequency/channel relationships.

The PRO-96 doesn't do LTR at all. The PRO-97 can read idle bursts and get the repeater number from them. Only about half the LTR systems here use idle bursts so that doesn't always work.

The downside is that it is more prone to miss LTR transmissions from what I have read.

The PRO-97 should track ok since it uses the repeater numbers. The older PRO-92 was inferior as an LTR tracker and it did not use the repeater numbers for tracking.

The best way to attack an unknown LTR system is using LTRDUMP. Repeater numbers for GOTO, HOME, and FREE are all displayed for every transmission.

I've gathered all the information I could find on LTR and put it in a file at http://home.hvc.rr.com/bpetrow/ltr.htm

 

[W4UVV]

LTR reply

Do a search of the FCC database for your state. Typically LTR system repeater outputs are in the 451.0125-464.9875 mhz. range. I assume you have a decent scanner and outside antenna system. You will have to do some research but it is doable given enough time monitoring.
For example starting from a zero information baseline I would tune the above frequency range listening for a LTR unmodulated carrier(no audio-actually a subaudible tone) that keys periodically approximately once every 8-10 seconds. I would note that frequency and do an FCC database search for all users of that frequency in state. Then I would site check the licensees for typically a radio service provider in my general area. I would check the licensee information for each one of interest and look for the type of operation. If it is "FB2" that usually means it is a standalone dedicated or community repeater operation, not LTR. However, if it is "FB4, FB6, or FB8", that is a good clue that the operation is LTR.
I would write down those licensee callsign frequencies and check each one to ascertain whether or not a unmodulated carrier keys as previously described. All system frequencies may or may not be used in an LTR system even though licensed. If no unmodulated carrier keys then possibly it is a frequency for whatever reason not currently active in the system. Subsequent to confirming the active frequencies in the system follow the instructions given in the magazine article as to process aiding in determining the correct logical channel programing sequence. It can be frustrating and time consuming but that's reality. The BC796D must be programed in the correct logical channel sequence for it to track the LTR signals properly. Remember also one of more of the LTR frequencies may be shared with another licensee who is not a LTR system user.

Ok. read PRO97 vice PRO96. I don't have either radio but I have read the RS digital scanner did track LTR transmissions correctly but the tradeoff was a higher rate of missed signals.

I haven't heard of LTRDUMP. I'm for anything that makes identifying LTR signals easier.