LTR comms off 2 towers simultaneously?

[mr_hankey]

tonight, i heard Jim's Catering off the South Town Tower on 452.4250.

it was an id of 0-08-040.

the odd thing is that i SIMULTANEOUSLY heard the exact same comm from Jim's Catering off the North Town Tower on 463.0000 (the towers are over 13 miles apart).

there was no id associated with the North Town Tower because i was just scanning frequencies off that tower in non-trunked mode with the 2nd radio.

so i had 2 trunk trackers, one tracking the South Town LTR tower and another just scanning frequencies associated with the North Town LTR tower and heard a "simulcasted" LTR comm.

what does that tell me about the LTR network that i am trying to unravel?

 

[grant]

Simulcast on LTR

My apologies about how long before I read this entry

I have seen and heard the same thing on Sydney Tower and Dural 490Mhz LTR sites.

A transport company will appear on Sydney Tower with 0-02-008 id and simultaneously transmit on Dural site with 0-01-008.

I am also aware that users roam from site to site when they are move around in the metropolitan area

Unfortunately the user 008 has stopped - I suspect they have now set up their UHF conventional frequency network in order to utilise the latest data tracking technologies, based on who I think that company was.


Grant

 

[ericcarlson]

My understanding is that LTR (regular) offers no real "roaming" capabilities. In order to roam on a multi-site LTR regular system the user has to physically change channels on their radio when they move into range of another site so that they are using a talkgroup on the other site. Each site operates independently. The talkgroups have to be hard-patched together (I presume this is done via telephone circuit most often).

Based on my monitoring, that is how "roaming" works on Houston area LTRs.

-Eric

 

[Cameron314]

My understanding is that LTR (regular) offers no real "roaming" capabilities. In order to roam on a multi-site LTR regular system the user has to physically change channels on their radio when they move into range of another site so that they are using a talkgroup on the other site. Each site operates independently. The talkgroups have to be hard-patched together (I presume this is done via telephone circuit most often).

Based on my monitoring, that is how "roaming" works on Houston area LTRs.

-Eric

I think that PassPort LTR systems allow roaming.

 

[grant]

regular LTR "roaming" capability?

Eric

Maybe "roaming" is an unfortunate word to use, perhaps scanning site channels is better. On the 800Mhz LTR sites they appear more rigid on which sites they use. However I have heard 490Mhz LTR site users moving to and from different sites discuss that they are scanning channel 1 , channel 2 etc. I have noticed that some users may appear on up to 3 sites. The system maybe setup to "vote" to the strongest site signal, depending upon their location.

That is how the cops here do it on their conventional non-trunking system ... in the hilly parts of Sydney, the motorola radios vote to the strongest signal.


Grant

 

[Brian73]

regular LTR "roaming" capability?

Grant and Eric,

I can answer for the systems in Sydney for certain as I used to program them up and work on those systems (well the 800 MHz at least).

On the 800 Mhz LTR it was all stand alone single sites. All radios in an operators fleet would be programmed the same. The only real difference being that we used to set the base radio on scan, scanning an inner City site and an outer City site. Obviously we used to set these bases up with Yagi antennas so they could get into the outer site and we used to wind the power down on base to 1 or 2 watts (trigger station). The operators were told not to use their radio on scan, but rather choose the best system for them to use (either in the City or as they moved West, the Western site). This way the drivers were usually on the right channel to hit a site while they were mobile and the bases would scan both channels. As Grant can testify to none of these operators are very busy.

The new 490 MHz LTR systems are not Multi Net, but appear to have one or two users on them that are similcast. By what means I'm unsure. It may be a link to similcast them or something different. There are also a couple of users that are not similacast but the base transmits on two sites at once and the mobile once again choose the best site for the area they are in.

This probably doesn't explain too much, or anything new, but it sets firm what Grant is hearing.

Brian.

 

[KC5MAI]

Sounds like a Passport system using LTR. With Passport all sites can be linked together via t1 lines or microwave. It sounds like the ltr users you are talking about are on a Passport system set up for LTR and you just might have Passport radios on the system soon. We call this LTR networking. The information is programmed into the switch at the sites as to which ID at which site is connected to which ID at the other sites.