LTR PassPort Traffic on Regular LTR Channels

[dtscho]

For this question, I'm referring to this system:

http://www.radioreference.com/modules.php?name=TRSDB&sid=3394

(I'm using a BC246 and a BC780.)

This system appears to have three regular LTR home repeaters, and one PassPort home repeater. When the PassPort home repeater has more than one user talking at the same time, it "trunks-out" to one of the regular LTR home repeaters. When this happens, I see an ID on the screen (even though it's supposed to be a PassPort user). When the user is on the PassPort home repeater, I don't see an ID, since it's a PassPort channel.

Is this the way regular LTR/PassPort LTR usually works? My understanding was that if a user was PassPort, an ID for them would not show up, no matter what repeater they used. Is it possible this system is not PassPort, but one of the other "flavors" of LTR?

I know this is kind of a complicated question, and I'd be happy to clarify if any of it isn't clear. Thanks in advance for any help.

Dave

 

[EricCottrell]

Hello,

What are the IDs?

My understanding of a mixed system is that Passport Home Channels only have Passport and Regular LTR Home Channels only have regular LTR. It is the overflow (non-homed) channels that can be either.

Since Passport and LTR share the same bit rate it is possible that certain Passport data will be incorrectly decoded by a Regular LTR scanner and this is what you are seeing.

It is also possible that there is a way for Passport to show up on a Regular LTR home channel. Besides the real Passport data there could be dummy Regular LTR data to indicate the channel is busy. Any channel redirects for Regular LTR users of the channel would have to be in Regular LTR as well.

If someone in the area could run LTRDump on the system it would help sort it out.

73 Eric

 

[dtscho]

Eric,

Thanks for your ideas. There don't appear to be any channels used only for overflow in the system. There are three regular LTR home repeaters (1, 5, 9) and one PassPort home repeater (13). When there are two users trying to talk on 13, the system will trunk-out to one of the regular home repeaters. When 13 is free again, the user will go back to it.

(There aren't any IDs in the database because RR doesn't allow unidentified info, and I haven't identified users yet, just the home repeater numbers.)

I don't have LTRDump capability; maybe someone else in the area does...?

Dave

 

[hkrharry]

with pass port you have home, collect, & goto channels.
on LTR you have home & goto channels.
if a channel is a passport home or collect it cannot be a home or goto for a LTR channel.
and a LTR home channel cannot be a Passort channel
but you can have a goto channel used for both passport and LTR.
so watch your LTR dump carefully and you will find out what channels are homes and goto's.
the PP home and collect are chirping rapidly about every 2 to 3 seconds, a LTR home can chirp every 10-13 seconds or not at all.
the goto channels dont normally chirp at all.
.
on passport your radio normally registers on the home channel of its home system, if it is out of range of its home area then it registers on the collect channel. the collect channel is for roamers. each radio builds a almanac of the home systems & neighbors it hears when moving about the PP system and then hands off to the strongest system it can access.

hope this helps

sm0ke

 

[dtscho]

The channel that I think is PassPort (490.1875, home repeater 13) gives the "chirp" about every eleven seconds, just like what a regular LTR channel should do. By the way, the other three channels chirp every eleven seconds as well.

Dave

 

[dtscho]

Another interesting thing about home repeater 13, the one I think is for PassPort: on the BC246, when holding on the frequency (not while in ID Scan or Search mode), the IDs will briefly show on the screen. They won't show for the whole time of the transmission, like with regular LTR IDs, just for a second or two. (This does not occur on the BC780.)

I'm beginning to think that maybe this home repeater is regular LTR, and the scanner can't handle the LTR datastream for some reason...? I don't know, I guess we really need someone to run LTRDump on the system to figure out what's going on.

Dave

 

[dtscho]

Could the home repeater (490.1875) that's not decoding the LTR on the scanners be LTR-Net? The Wiki doesn't have much on this "flavor" of LTR, but it does say that it's compatible with LTR Standard, which would seem to be a plausible explanation of this situation.

So I guess the question is: if one is trying to "decode" an LTR-Net system or channel with a scanner, would one see an ID occasionally, and then it might go away? If this is the way it works, then I think there's a strong possibility that this system is using LTR-Net.

Incidentally, with the Loudoun County, VA public schools system (http://www.radioreference.com/modules.php?name=TRSDB&sid=2798), I believe I saw LTR IDs pop up every now and then, even though that system is supposed to be LTR-Net.

Thanks,
Dave

 

[grem467]

With multi-net, you would have a channel in the system that is always keyed. It would sound like a dead carrier, but it carries the subaudible control data. In the system near me, this channel can also be used for voice as needed.

 

[EricCottrell]

Could the home repeater (490.1875) that's not decoding the LTR on the scanners be LTR-Net? The Wiki doesn't have much on this "flavor" of LTR, but it does say that it's compatible with LTR Standard, which would seem to be a plausible explanation of this situation.

So I guess the question is: if one is trying to "decode" an LTR-Net system or channel with a scanner, would one see an ID occasionally, and then it might go away? If this is the way it works, then I think there's a strong possibility that this system is using LTR-Net.

Incidentally, with the Loudoun County, VA public schools system (http://www.radioreference.com/modules.php?name=TRSDB&sid=2798), I believe I saw LTR IDs pop up every now and then, even though that system is supposed to be LTR-Net.

Thanks,
Dave

LTR-Net was developed to have features of Multi-Net and backwards compatible with Regular LTR. It does it by using values that are not valid in Regular LTR (using repeater numbers over 20, etc) for the new features.

Around here there are LTR-Net sites for Cox Cable down in RI and CT. Repeater 20 is continously on the air sending the idle group (0-20-255) and is the backup home channel. It carries all the site activity and can have voice on it like a Multi-Net system.

I do not remember scanning a LTR-Net system with my Scanner. With LTRDump I see regular LTR talkgroups come up. One difference is the CW-ID is usually group 254 on a LTR-Net system and group 253 on a Regular LTR system.

73 Eric