TRBO Frequencies not represented correctly

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ka3jjz

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I've been trying to build a form based on a wiki template to display frequencies, slots, color codes and other data for Mototrbo trunked systems that have multiple color code data in the database.

However it seems I've been doing something wrong. I've been copying the database freqs where needed, and it appears that it's using a LCN as a place holder for the slot number, instead of an actual channel number.

Case in point:

Communication Specialists (Capacity Plus) Trunking System, Various, Virginia - Scanner Frequencies

Note the Fredericksburg site. It repeats frequencies twice to, I assume, represent slots 1 and 2. However when you start getting more than 1 set of channels, that representation falls apart like wet tissue paper.

Fortunately my template is pretty easy to edit, and I'm going to have to go back and fix the articles I've written (not too many). But the database is another matter; this representation is incorrect, if I understand how TRBO works. Granted that no scanner can handle TRBO, but it's really unnecessarily confusing to the newcomer. and as for programming a real TRBO radio, would they actually have to repeat the frequency twice just because of the 2nd slot? Seems unnecessarily sloppy and prone to errors...

How about just listing the frequencies 1 time, and add a notation that each frequency occupies 2 logical slots? Or are you guys planning to add a new form to the db to correctly display TRBO data?

Mike
 
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Voyager

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How about just listing the frequencies 1 time, and add a notation that each frequency occupies 2 logical slots? Or are you guys planning to add a new form to the db to correctly display TRBO data?

It seems RR is confusing LCN and timeslot as one in the same thing.

On your sample system, each LCN should be listed once.

I.E.:

001 (1) Fredericksburg - Confirmed LCN Spotsylvania 01 451.93750 02 452.23750 03 452.73750


Since it's 2-slot TDMA, users should know there are two slots on each LCN.

A system local to me just changed from LCNs 1/2/3/4 to 1/3/5/7 which makes things even more confusing since you have to add 1 and divide by 2 to get the real LCN. Most programs will show LCN1/Slot2 or LCN3/Slot1.

On the Color Code, I wonder if it can be added to the location, such as:
Fredericksburg (CC14)
 

KG4INW

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Granted that no scanner can handle TRBO, but it's really unnecessarily confusing to the newcomer. and as for programming a real TRBO radio, would they actually have to repeat the frequency twice just because of the 2nd slot? Seems unnecessarily sloppy and prone to errors...
For conventional programming, yes, two separate channels can be identical except for the time slot. Users wouldn't know they're using the same frequency. However, for trunking, the repeaters are added to a channel pool and individual talkgroups are programmed separately (but they can then utilize any talk path available at the moment).
 

ka3jjz

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This should be a somewhat better example of a TRBO system - each channel is listed twice (for the 2 slots) with separate entries

Horseshoe Casino (MD) DMR Bandplan - The RadioReference Wiki

Unfortunately this is likely to require a somewhat significant db change (new form, new mapping). To me, at least, some sort of interim solution that properly represents the freqs in a TRBO trunk system is needed. The way it's being done now is not accurate.
 

ka3jjz

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One part of any interim solution should be using the correct form - it seems that when the TRBO freqs are entered, they're using the LCN based forms for EDACS and LTR systems.

If the plain Motorola forms were used, at least you wouldn't have the misleading LCNs listed along with the frequencies.

Mike
 
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DaveNF2G

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I think the term "LCN" is being misapplied with respect to the TRBO systems.

The "logical" channel number would be the one assigned to a particular slot in a signal that is being transmitted by a particular repeater. Each repeater carries two LCNs.
 

ka3jjz

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On second thought, it might be slightly better to use the form used for Phase 2 Moto systems - then change the warning message to say that no scanner can hear this system.

It too doesn't use the LCN format that's so misleading, and it's a bit closer to what is needed...Mike
 

KG4INW

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I definitely see how trying to represent a TRBO system (especially Cap +, linked Cap + or Connect + systems) in the database as it is can lead to confusion. Having programmed a number of TRBO radios for various systems (as an MSS tech), I think that the only time you'd need to duplicate frequencies is when you're showing conventional channels.

All of the trunking systems that I've worked with (and I'm still learning so keep that in mind) it's been a given that you will at some time be on any given repeater on any given timeslot. For example, if you have 3 repeaters, you have 6 talk paths and radios on the various talkgroups will trunk to whichever one is available at that time. Otherwise, if all 6 paths are in use, you get a system busy.

Perhaps you could have a note that explains all repeaters (in a trunked TRBO system) have two timeslots and any can be in use at any time. I think listing just the system freqs should be all that's needed.

Where it's necessary to differentiate is on conventional systems (simple repeater or conventional linking as with IP Site Connect) because two different channels can use the exact same frequency but have a different timeslot. Again, transparent to the users thanks to TDMA but necessary for programmers.

I hope I've helped!
 

Voyager

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I think the term "LCN" is being misapplied with respect to the TRBO systems.

The "logical" channel number would be the one assigned to a particular slot in a signal that is being transmitted by a particular repeater. Each repeater carries two LCNs.

No, a channel is a frequency whether you are talking EDACS, LTR, or TRBO.

No, a system using four frequencies has 4 LCNs with each having two slots. It has 8 talk paths (provided no control - 7 with control)

LCN 1 - Slot 1
LCN 1 - Slot 2
LCN 2 - Slot 1
LCN 2 - Slot 2
LCN 3 - Slot 1
etc.

On the updated example, I have never seen a case where two slots on the same channel have different color codes. That table could get messy when you get into 4-slot TDMA or higher. As it is, it has redundant info, as there is no need to list each slot.

Just KISS - list the Site containing the LCNs with Frequency, Color Code (or RAN), and Comments:

Baltimore:
01 7 461.3500 ?
02 8 462.1000 ?
03 9 463.3000 ?
04 10 463.6000 ?
05 11 463.9250 ?

OK, that didn't format well...

If it's TDMA, the multiple slots is implied. The system type will specify how many (such as MotoTRBO having 2 slots). Don't make it more confusing. A P25 Phase II system has multiple slots, but the frequencies are not duplicated in the channel list, nor need they be. Why make TRBO different? (aside from simply adding the small LCN number)
 
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Voyager

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On second thought, it might be slightly better to use the form used for Phase 2 Moto systems - then change the warning message to say that no scanner can hear this system.

It too doesn't use the LCN format that's so misleading, and it's a bit closer to what is needed...Mike

So just add the small LCN to each frequency ala LTR/EDACS. Don't try to re-invent the wheel. There is enough of that around.
 
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DaveNF2G

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No, a channel is a frequency whether you are talking EDACS, LTR, or TRBO.

I'll accept your explanation and expertise.

Theoretically, a "channel" is everything that constitutes a talk path. In TCP/IP terms, my definition of LCN would be closer to the ideal. Obviously, trunked systems are not designed around TCP/IP, so I'm not disputing your point. :)

On the updated example, I have never seen a case where two slots on the same channel have different color codes.

I haven't even seen a single system with multiple color codes. In any case where my equipment showed that, it was because of signal reception errors. Improving reception eliminated the variant color codes from my logs.
 

com501

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Every system I build, each RF frequency has a different color code. Every channel in the combiner has a different color code simply because it makes my life much easier to identify any 'crap' emitting somewhere else. I can see what the color code is and figure out where it came from. Plus it keeps people busy trying to figure out how to copy the system accurately and 'bootleg' on it (good luck with that).

You are absolutely correct in that Trbo (DMR) is NOT CAPABLE of producing a different color code for each time slot per RF frequency.
 
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