LTRtrunk Getting BadCRC Messages On LTR Passport

[KD4YGG]

A couple of weeks ago I tried to run LTRtrunk on Montgomery County, Tennessee's LTR Passport public safety system.

Although there was success on the sister government services Passport system, I got a lot of BADCRC message running LTRDump. LTRtrunk never would show anything although I could hear transmissions.

Any ideas? I'm thinking I may have been too far from the transmitter site to get a good signal.

Thanks

 

[EricCottrell]

Hello,

Some of the CRC values were guessed at. I suspect that the DCC (like the area bit in regular LTR) of the system is 2 or 3. Please send me any LTRDump.txt files from the system with the CRC errors.

It could be signal levels but it is just as likely I guessed wrong.

73 Eric

 

[KD4YGG]

Here ya go!!!

 

[EricCottrell]

Hello,

Thanks for the files. It helped alot. I need more people to log systems and send me files.

The decoding looks pretty good on all three files. This is a three site passport system. Sometimes the system comes up without voice to transmit data. The unknown type 1 are system messages likely acknowledging something. Unknown type 11 is registration.

montgov1 is site one of the system.
Neighbors are 461.6375 (931) and 461.6875 (935)
Frequency you were listening to was 451.400 (112)
Other frequencies at the site are 451.7 (136), 451.95 (156), 452.775 (222), 453.475 (278), 453.725 (298), 453.775 (302), and 461.25 (900)

montgov2 is site two of the system
Neighbors are 451.3 (104) 461.6875 (935)
Frequency you were listening to was 461.6375 (931)
Other Frequencies are 462.0125 (961), 463.3875 (1071), and 464.8125 (1185)



montgov3 is site 3 of the system
Neighbors are 451.4 (112) and 461.6375 (931)
Frequency you were listening to was 461.6875 (935)
Other frequencies are 462.0 (960), 463.3625 (1069), 464.8375 (1187)

What is interesting is it appears site 2 has an incorrect neighbor frequency programmed (451.3 instead of 451.4). This is not a problem if the proper seed frequencies are in the radio.

I would say the reason you were not picking up any units is due to monitoring the registering frequency and not the home channel. In listening to the system in CT I found that the registering frequencies are sent in the neighbor info and do not carry voice traffic . You need to scan the other frequencies at the site and find the home channels.

I find that a site will have a registering frequency, home frequency for units homed at the site, and roaming home frequency for units homed at other sites. On the CT system these are three different frequencies.

73 Eric.