GMRS trunking system?

[Lscott]

I don’t recall seeing this topic covered. Has anybody seen a “trunked” GMRS repeater system?

https://en.wikipedia.org/wiki/Trunked_radio_system

Several of my radios have “LTR”, logical trunked radio functionality builtin. There is also such a thing as LTR-Net which networks several trunked repeater systems together.

https://www.twowayradiodirectory.com/ltr.html

I know this requires several repeaters and there are only 8 channels reserved for repeater use so it is resource intensive. People are networking GMRS repeaters together so a trunked system isn’t that much more of a stretch.

[tweiss3]

Well now this is a very interesting proposition. I can't find the emissions designator for analog LTR trunked systems, but it might align with the code. LTR, along with other trunked systems use multiple repeaters per site, so you could in theory use a 4 repeater system, say 19, 20, 21 & 22 repeater pairs and LTR trunked will automatically re-route to the open pair for your specific talkgroup. My understanding of LTR is that there isn't a control channel, the control data is a burst included in the voice channel, and you stay on the frequency you are on, unless the data burst indicates a change. Now that being said, you would tie up more than 1 repeater pair, but if you were do an area wide linked system to cover an entire county or region, and worked with other users, who cares?

 

My TK-8150 does LTR, but I have no use for it, unless its in this specific instance, which might be useful, but expensive to put out the backbone (multi-antenna, multi-repeater on really large tower), just to "stay within rules of GMRS". I don't have a for sure answer if this is within the rules because I don't have the time to research, but it seems the closest to be within the rules as written. Again, trunked systems are designed so multiple groups of users can better co-use the frequencies. In my area it wouldn't make sense, but some place with high usage it might.

 

DMR almost makes more sense (or P25P2), since it TDMA and has 2 voice channels per frequency pair, but that's another argument.

 

You poise a very interesting question. I will have to research more later.

[JohnE]

LTR falls w/in the rules as far as sub audible tone goes, its no different than tone/DCS as it is under 300 cycles.

now doing  multiple machines linked together as a system is another story. 

W/8 channels so close in frequency each machine would have to have its own filters and antennas if it were done at a single site.

you would have to have some really heavy use to warrant that kind of set up.

Quote

My understanding of LTR is that there isn't a control channel, the control data is a burst included in the voice channel, and you stay on the frequency you are on, unless the data burst indicates a change

in LTR there is a home rptr # ,area bit, and the encode/decode data. all the steering is done by the controller.

did this yrs ago when I had some trolls playing w/my machine a little too much. I made it switchable form conventional to LTR over the air.

[Lscott]

14 minutes ago, JohnE said:

in LTR there is a home rptr # ,area bit, and the encode/decode data. all the steering is done by the controller.

did this yrs ago when I had some trolls playing w/my machine a little too much. I made it switchable form conventional to LTR over the air.

Never though about using LTR as a means for repeater access control while ignoring the multi-repeater bit. That would seriously screw with repeater jammers and unauthorized users.

[JohnE]

Quote

Never though about using LTR as a means for repeater access control while ignoring the multi-repeater bit. That would seriously screw with repeater jammers and unauthorized users.

that is why I did it

 

[Lscott]

The legal basis I’m not so sure if it would pass under the FCC rules. This is my reason for asking if anybody knows of such a system in operation with the FCC’s blessing.

The radios are transmitting digital data using sub audible signals to the trunking system’s repeater. Also what I read the repeaters are sending digital data out every 10 seconds on an open channel. See the links in my opening post.

The FCC has some requirements, limits, on the duration, frequency and type of digital data that can be transmitted. Somehow a burp of digital data every 10 seconds will effectively preclude having another conventional repeater on the same channel. I don’t think this would be compliant with the rules.

[JohnE]

the "pulse" can be turned off on some controllers.

[n1das]

On 7/6/2021 at 8:06 PM, Lscott said:

Never though about using LTR as a means for repeater access control while ignoring the multi-repeater bit. That would seriously screw with repeater jammers and unauthorized users.

I've thought of doing this but don't have any LTR capable radios.  It would be set up as a single channel LTR system and with the pulse turned off.  I have heard of exactly this being done to thwart repeater jammers and unauthorized users.

I've thwarted a well known jammer in the past by using DCS/DPL instead of CTCSS/PL.  The jammer in this case had antiquated radios that only had CTCSS/PL capability and no DCS/DPL capability.  He also didn't have a clue about DCS/DPL.  I've heard him screaming on the air about being unable to get into my repeater.  He was continually p!$$ed about not being able to get into the repeater after trying almost every CTCSS/PL tone.  I've heard  of DPL also being referred to as "Definitely Prevents Losers" LOL.  This won't work today with most modern radios having DCS/DPL in addition to CTCSS/PL.

 

[Lscott]

15 hours ago, n1das said:

I've thought of doing this but don't have any LTR capable radios.  It would be set up as a single channel LTR system and with the pulse turned off.  I have heard of exactly this being done to thwart repeater jammers and unauthorized users.

I've thwarted a well known jammer in the past by using DCS/DPL instead of CTCSS/PL.  The jammer in this case had antiquated radios that only had CTCSS/PL capability and no DCS/DPL capability.  He also didn't have a clue about DCS/DPL.  I've heard him screaming on the air about being unable to get into my repeater.  He was continually p!$$ed about not being able to get into the repeater after trying almost every CTCSS/PL tone.  I've heard  of DPL also being referred to as "Definitely Prevents Losers" LOL.  This won't work today with most modern radios having DCS/DPL in addition to CTCSS/PL.

 

Some of the Kenwood radios I have with LTR are:

TK-3140

TK-3173 (Same radio as TK-3170 but with trunking.)

TK-3180

All have Part 95 certification.