Digital Voice Mode on GMRS - Possible Rules?

[Lscott]

I was thinking here tonight about digital voice modes on GMRS. I’m sure it will happen sooner or later. What I haven’t seen is a good discussion on how it should be done. If there is any chance the FCC would be receptive to the idea then a good reasoned plan on the implementation I think would help push it along.

So what would be a reasonable plan be and what mode(s) make sense? I’m going to guess the one thing the FCC won’t do is expand the spectrum. They might would entertain splitting existing 25KHz channels into two 12.5KHz or four 6.25KHz ones.

[gman1971]

I'll bite!  

Well, since GMRS/FRS is meant to be "easy to use" I'd say replicate what the DTR radios on the 900mhz band are doing. Set a 16-bit or 20-bit pseudo random FHSS sequence and have them hop in the upper 12.5kHz of every wideband GMRS channel, and use the whole 12.5kHz for the FRS channels.

IMO. it doesn't get any simpler than that. Eiter 65k channels, or 1M channels, depending on 16 or 20 bit for the random FHSS sequence.

G.

[Lscott]

That’s not a bad idea.

I was thinking along the line of using the nearly useless narrow band channels 8 to 15.  Currently at 0.5 watts many GMRS radios don’t even include them. If the digital mode was restricted to  those channels at 2 to 5 watts and 6.25KHz bandwidth the interference to the adjacent wide band repeater channels would be minimal.

[Lscott]

Using 4FSK I think would be easier than a FHSS. A standard would have to be established so all radios could communicate with radios from other manufacturers. Then you need companies like Motorola to open up their proprietary design they use on their FHSS radios. I’m not confident they would entertain that idea.
 

With 4FSK at least two standards already exist, NXDN (primarily USA) and dPMR (primary European Union). Both are “true” 6.25KHz technologies. Either one would be suitable to use. More than one company manufacturers radios for each of the above already. Also the FCC has moved into splitting 12.5KHz channels into two 6.25KHz.

I would vote for NXDN since it widely used in the US already in various sectors. Used commercial radios are not terribly expensive either. In fact, for example, the NX-300’s in the 450-520 band split have FCC Part 95 certification already. They can do wide and narrow band FM along with narrow band digital (12.5 KHz) and very narrow band digital (6.25 KHz).

NXDN White Paper.pdf DA-12-10A1.pdf

[gman1971]

I think you are confusing 4FSK and FHSS. You can FHSS in any modulation, be it FM... SSB, etc. 

Anything narrowband will just run into the same service (22 channels) problems we are facing right now: interference and band congestion/saturation, and that includes NXDN too which is still narrowband BTW, and it doesn't matter how much narrowband it can get. At best, if all channels were to be split in 4 (or 2), you'll only get a few additional channels over the pre-existing 22, and that would be assuming the FCC ever makes 6.25kHz mandatory, which we both know it won't happen. So its a waste of time to provide the least efficient RF digital format there is. TDMA 2-slot offers double the spectral efficiency over a single 12.5kHz, and please, spare me the BS about you being able to split a channel in 2... hahaha, with what filters? 600kHz split in Ham repeaters already requires 6" cans the size of oxygen tanks.... Then, even if all channels were split in 6.25 chunks, that will only provide roughly 88 channels... at best... vs a 1 Million interference-free channel pool with a properly implemented 20-bit FHSS scheme.

In addition to that, FHSS also provides other benefits that NXDN simply can't and will never be able to afford: far superior spectral efficiency, slightly better range (due to frequency hopping, (if one particular frequency is blocked, the next hop frequency might not), very strong interference resistance, a good deal of privacy against casual eavesdropping, and all that without the use of the big no-no word called "encryption."

Using narrowband and analogue stuff is the way of the dinosaurs. DMR is also narrowband but its saving grace would be its using a TDMA (Time Division) scheme, and can do something that NXDN will never be able to do: Have 2 concurrent conversations over the same single 12.5kHz channel. I think its called 6.25kHz equivalency...

With that said, and for as much as I am invested in DMR, I would rather see the implementation of an open FHSS (ETSI/ANSI) standard instead.

G.

[Lscott]

My point, and goal, with this thread are possible rules that would allow digital voice to be used within the current confines of the spectrum currently allocated to GMRS operation. The chances of the FCC adding spectrum is nearly zero. 

The prior attached file shows the FCC has allowed splitting existing commercial channels into narrower allocations. The same could be done with GMRS all without adding additional spectrum. On the other hand there would be a gain of some extra simplex channels. The practicality of close by stations operating on adjacent 6.25KHz channels is another point. Of course if the stations are geographically separated it likely won’t be an issue.

While DMR has some good points it does require coordination between radios utilizing the same frequency to take advantage of DCDM. The occupied bandwidth is still 12.5KHz regardless if one or two slots are used. The 6.25KHz is only an “equivalent” due to the dual slot nature of the transmissions. Trying to squeeze a DMR signal in between let’s say the main repeater channels is exactly the same as the current low power, and basically useless, FM 12.5KHz ones. I was thinking that a true very narrow band digital signal might be used there while resulting in even less interference and and maybe at a higher power for simplex operation.

At the moment both NXDN and dPMR are both established digital protocols. There is no necessity to try and standardize a FHSS CAI. This is a necessity if there are going to be multiple manufacturers of these FHSS types of radios. And of course they will have to communicate among themselves too. Utilizing one of the above, NXDN dPMR, is a known standard with lots of field experience and one less item for the FCC to use as an excuse to claim it isn’t proven or accepted by the market place or can’t coexist with current FM technology.

 Now about DMR, I like it. Yes it can be used however I don’t see how without dedicating specific channels to it. That of course would tick off the FM only users. So the big question is where do you put it or just make it the Wild West and let the users fight it out. The other advantages are the reduced average power, great for hand held radios, and the single frequency repeater operations. Given the number of times you see people asking about setting up their own repeater this would make it almost brain dead simple to do, and no special equipment like tuned cavity filters to deal with.

[gman1971]

How are you arriving to this conclusion about needing more bandwidth?

A 12.5kHz channel FHSS scheme over whatever GMRS bandwidth already has currently allocated won't require any additional spectrum to be allocated. So I am not sure what is it you are talking about.

Next point: this is not a NXDN vs DMR as you'd like it to be.... and then to reiterate this AGAIN, b/c you seem to just ignore the fact that I am NOT endorsing DMR as a potential GMRS digital modulation, so please pay attention to what I am saying before lecturing me about how super-duper NXDN is, well let me tell you: that is your opinion, and you are entitled to that. I don't agree with it, and I find NXDN totally useless and lacking for many reasons, and certainly for the purpose of de-congesting the GMRS allocated bandwidth.

So, I'll state this once again: FHSS, (or DSSS), is the best way to go in so many ways: avoids pissing other users off with random lids barge into your conversation, or hijacking repeaters... etc, and you get 1 MILLION channels, that is: 1,000,000 channels.... no amount of NXDN voodoo BS is going to compete with that.

Maybe you don't understand what FHSS really is?

Again, you just can't beat that kind of spectral efficiency of an FHSS scheme with anything single-channel narrowband like DMR/NXDN/TETRA/P25/<insert your single channel narrowband modulation name here>. The RC world has been doing this for almost 2 decades now, where you can have dozens of models flying simultaneously next to each other without interfering each other... well, don't try that with any single-channel narrowband stuff...

G.

[gman1971]

You never answered this question: Do you know what FHSS is?

[Lscott]

Yes I have a basic understanding of the concepts. I have some material on it in my personal library. The first photo is a section out of one of my books on digital satellite communications. It’s also allowed in amateur radio by the way. That’s the second photo.

[gman1971]

Not sure what to say, but a couple of pictures of a book doesn't show me understanding of the concept, but that's fine.

In a nutshell: FHSS is a Frequency Hopping Scheme, or Frequency Hopping Spread Spectrum: which could be considered a combination of FDMA (Frequency Division, Multiple Access) and TDMA (Time Division, Multiple Access) in one package. Transmits for a few milliseconds on a given frequency, then it hops to another frequency and transmits again, rinse and repeat. Whatever frequency the radio will hop to next is determined by a random seed number, and a counter. So when both radios hop in the same pattern then you have a viable radio link, but when they do not, the two radios can't talk to each other, nor have a clue that another radio is even talking.

At any rate, my vote goes for FHSS, just like the DTR radios in the 900 Mhz band have already proven it works very well.

Again, I am also NOT endorsing Motorola radios either, just making a reference to their FHSS scheme.

Also, military grade radios use FHSS as well, for all (but not limited to) the reasons I've explained.

G.

[Lscott]

So the point here is how would you present this to the FCC as a proposed rule change(s)?

The FCC will likely take the path of the least resistance. That means if more of the work can be done by us ahead of time, anticipate possible objections etc. then have reasonable solid answers the more likely it will get serious consideration. In other words we have to do their job for them.

Don’t forget there will be others out there who likely DON’T want to see any changes. There is always that crowd and that has to be taken into consideration too.

Then you have the manufacturers that will likely chime in if they feel a competitor may gain an advantage depending on what selection is made, if any. Who knows the FCC could be persuaded to allow multiple digital voice modes. 

Based on how this is turning out I’m of the current opinion it was a mistake to even bring up the idea. The debate isn’t over personal preferences. There is nothing to be gained or to facilitate the goal here by trying to prove who knows more except to derail the idea. If others want to continue, fine. But I’m done with.

[gman1971]

Well, I'd say however it was done to get the 2.4 GHz ISM band for WiFi, BT, BT Intercoms, etc... that is probably what needs to be done to the GMRS service as well.

The devices themselves (no user input) negotiate handshakes, packet collision, etc, and leave the user to just select whatever "channel" among a large pool of "channels", whether these channels being "physical" channels or "virtual" channels, and some privacy codes.. etc.

There is/was nothing personal about stating that FHSS is a better scheme for spectral efficiency than any narrowband single-channel modulation, including FM, NXDN, DMR, et. all.

An open standard will need to be implemented for this, be it an ETSI standard, or be it ANSI standard. whatever, It just cannot come from a single manufacturer, and that includes Motorola, Kenwood, et. all.

G.

[WRQD721]

On 6/5/2022 at 10:55 PM, gman1971 said:

Not sure what to say, but a couple of pictures of a book doesn't show me understanding of the concept, but that's fine.

In a nutshell: FHSS is a Frequency Hopping Scheme, or Frequency Hopping Spread Spectrum: which could be considered a combination of FDMA (Frequency Division, Multiple Access) and TDMA (Time Division, Multiple Access) in one package. Transmits for a few milliseconds on a given frequency, then it hops to another frequency and transmits again, rinse and repeat. Whatever frequency the radio will hop to next is determined by a random seed number, and a counter. So when both radios hop in the same pattern then you have a viable radio link, but when they do not, the two radios can't talk to each other, nor have a clue that another radio is even talking.

At any rate, my vote goes for FHSS, just like the DTR radios in the 900 Mhz band have already proven it works very well.

Again, I am also NOT endorsing Motorola radios either, just making a reference to their FHSS scheme.

Also, military grade radios use FHSS as well, for all (but not limited to) the reasons I've explained.

G.

You will not see freq. hopping on GMRS or Amateur. If GMRS goes digital, it will go just like Amateur Radio did. Proprietary digital, proprietary digital, DMR, APCO P25. And when you hear it, you won't be impressed. At this point in the game, P25 has the best audio and is easiest on the ears (and that's not saying much).

[tweiss3]

7 hours ago, WRQD721 said:

You will not see freq. hopping on GMRS or Amateur. If GMRS goes digital, it will go just like Amateur Radio did. Proprietary digital, proprietary digital, DMR, APCO P25. And when you hear it, you won't be impressed. At this point in the game, P25 has the best audio and is easiest on the ears (and that's not saying much).

I agree, it will be one of the big 3 (DMR, NXDN or P25). If you get to listen to the big three setup correctly side by side, there isn't much of a difference. DMR being flooded with bad IP links, barely operational hotspots, and cheap radios does affect how it sounds. Local via repeater, on Motorola/Kenwood equipment only, you can't really tell the difference between the 3. P25 phase 2 does sound different, but that would never show up in GMRS, because that's a trunking only protocol. 

[KAF6045]

DMR, P25, and Yaesu System Fusion (maybe NXDN) use the /same/ AMBE vocoder; they just wrap the digital voice packet with different control header/footer. This is why many of the hotspots are capable of doing cross-mode operations: they strip off the source control header/footer and wrap the voice data with a header/footer compatible with the target system.

D-STAR uses a different AMBE vocoder -- doing cross-mode with D-STAR requires one to have AMBE chips that understand both formats, and (in essense, reality may stay digital realm) are converting one digital stream to analog, feeding that analog to the other vocoder to create the required AMBE format for the mode. The cost difference between an OpenSpot 4 and an OpenSpot 4 Pro is the AMBE chip/license.

[Lscott]

My comments are to long to type so read the attached file. As stated in the very first post the idea is what rule changes are required and the probability of of getting the FCC to consider the idea. I have ZERO interest in any lectures about the technical merits. That totally derailed this thread from the beginning and I'm not going there again. I debated even responding to this thread and decided to give it one last try.

I make no apology for grammar, punctuation, spelling etc. My aim was trying to get some ideas down.  

 

 

 

GMRS Digital Voice - 20221011.pdf

[dosw]

Don't forget about the long tail.

 

Any future where digital signals supporting 65k or 1M users on a frequency can be stomped on by bubble pack radios from Walmart transmitting on those same frequencies in analog, just won't work out. People are going to pull a set of FRS or GMRS radios out of their sock drawer five, ten, fifteen years from now and push "TALK" on the things, potentially disrupting a lot of people using a frequency for digital. It will take a long time to phase out existing FRS and GMRS radios.

 

Case in point: I've owned a few sets of FRS radios over the years. One set got lost by an airline losing a suitcase. Another set had one of the two handheld units stop working, and for some reason I tossed them both. But sitting in a drawer three feet from me right now is a Motorola T6300 FRS radio. It supports 14 channels, has 38 CTCSS tones, and has some scramble mode. Using that scramble setting is not legal under current FCC rules, but when the T6300 was marketed (twenty two years ago), it must have been ok. My T6300 was manufactured November 2000.

 

The point is that I have GMRS radios I bought within the past 30 days, but also a radio that is mostly compatible with my GMRS radios that is 22 years old. Let's say five years from now the FCC legitimizes digital transmission for voice over GMRS frequencies. I'll probably still have my 22 year old FRS radio, which will be 27 years old. And I'll probably still have the GMRS radios I currently own. But not just me. People all over the US have sets of these radios, and don't use them often enough to bother replacing them.

 

This is to suggest, if the FCC were to introduce a version of GMRS that allows for digital transmission, it's probably going to have to be on a different set of frequencies from traditional GMRS. Even if the FCC were to eliminate GMRS today, those radios are still going to be keying up for years to come.

[KAF6045]

In a way, CB has had that problem for half a century. Most CB units are 4W carrier AM-only. But the higher end units supported 12W PEP SSB. SSB is just noise on an AM unit. I believe (before it was taken over by southern rednecks with no information to transmit, just talking with barely any gap for anyone else to get in, and running illegal amplifiers [I'm fairly certain the sunspot cycle isn't quite to the stage where 11m skip is going from Georgia to Michigan]) a convention had developed that SSB users would stick to channels 34-40 (or something in that range).

And now the FCC is considering allowing FM signals in those 40 CB channels. Which, again, will be noise to AM and SSB users, just as AM and SSB will be noise to FM users.

[wrci350]

50 minutes ago, KAF6045 said:

And now the FCC is considering allowing FM signals in those 40 CB channels. Which, again, will be noise to AM and SSB users, just as AM and SSB will be noise to FM users.

Not considering.  Done deal.

[DONE]

First thing that will be considered is the level of interference with legacy equipment.  Since we are limited on bandwidth, FHSS is gonna be a no go.  The popping it will cause in the analog receive of the legacy stuff and the fact it will effect ALL the channels not just the selected channel I just don't see it happening.  The next logical thought IMO is DMR, using TDMA of a 25KC or 12.5 KC channel.  Implementation would be simple enough in the channels could be designated with an A and B.  Meaning CH 19 in digital would be 19A and 19B to split the two time slots per channel.  The branded name for DMR of course is MOTOTRBO in Motorola speak, but there are a large number of manufactures that make DMR radios.  This would basically DOUBLE the number of channels that could be accessed from a radio in the same allocated bandwidth for GMRS. 

But so would going to 12.5KC channel spacing.  Mind you the range would suffer greatly with going narrowband, but the interstitial channels between the repeater allocations could then become full repeater channels if the FCC was so inclined to make that change. 

The other thing that's possible since we DON"T have the non-proprietary technology requirement in GMRS that the hams have, we COULD petition for some level of Tier2 DMR functionality like trunking for area's that have significant GMRS use.  That would share 4 talk paths on 2 repeaters with a huge amount of possible group call designations (talkgroups).  But planning and cooperation from ALL users of the system and the system owner would be key to getting that to actually work.  But some level of a 'CLUB' membership with or without dues would almost be mandatory as the configuration of the subscriber radios and ID assignment for the individual radios would need to be controlled or it would simply be chaos.  Tier 2 DMR allows for proprietary trunking methods like Capacity Plus from Motorola that will ONLY work from a Motorola radio.  

P25, which I would actually prefer, does NOTHING for increasing bandwidth allocation, unless you went to a Phase 2 APCO25 standard.  But the requirements for that are radios that are thousands of dollars and back end equipment that would be in the tens of thousands.  So that is a pipe dream.  And linking P25 is FAR more complicated than linking analog or DMR.  DMR linking is simple, other than every device on the linked system needs a specifically assigned ID.  Call routing mandates this.  But outside of that, a Motorola repeater that is DMR has an Ethernet jack in the back.  You configure the repeater a certain way, and connect it to the Internet.  There has to be a C-Bridge somewhere as there is a hard limit of 15 repeaters that can be linked together with out the C-Bridge, but outside that, you can route talk groups with the bridge to limit the number of active repeaters by the talk group being used.  Meaning a TG (talkgroup) could exist for each state, region, or a nation wide group simply by routing the TG to the repeaters in the footprint of the TG designated area. 

Any of this would of course interfere with legacy analog equipment and communications in analog.  There would almost certainly need to be some level of restriction of what repeater pairs could be used and how far they would need to be placed apart from current analog repeaters to minimize interference.  DMR talks further, which increases the possibility of analog interference.    And while I am all for it, and the conversion for ME is as simple as going to the tower and reprogramming my repeater (running an MTR3000 on the 462.675 machine) if you look at the coverage footprint of 675 on the map, running an analog repeater in that footprint would be near impossible as my transmitted output would tear the analog receive up for those operators.

[Lscott]

1 hour ago, WRKC935 said:

First thing that will be considered is the level of interference with legacy equipment.  Since we are limited on bandwidth, FHSS is gonna be a no go.  The popping it will cause in the analog receive of the legacy stuff and the fact it will effect ALL the channels not just the selected channel I just don't see it happening.  The next logical thought IMO is DMR, using TDMA of a 25KC or 12.5 KC channel.  Implementation would be simple enough in the channels could be designated with an A and B.  Meaning CH 19 in digital would be 19A and 19B to split the two time slots per channel.  The branded name for DMR of course is MOTOTRBO in Motorola speak, but there are a large number of manufactures that make DMR radios.  This would basically DOUBLE the number of channels that could be accessed from a radio in the same allocated bandwidth for GMRS. 

But so would going to 12.5KC channel spacing.  Mind you the range would suffer greatly with going narrowband, but the interstitial channels between the repeater allocations could then become full repeater channels if the FCC was so inclined to make that change. 

The other thing that's possible since we DON"T have the non-proprietary technology requirement in GMRS that the hams have, we COULD petition for some level of Tier2 DMR functionality like trunking for area's that have significant GMRS use.  That would share 4 talk paths on 2 repeaters with a huge amount of possible group call designations (talkgroups).  But planning and cooperation from ALL users of the system and the system owner would be key to getting that to actually work.  But some level of a 'CLUB' membership with or without dues would almost be mandatory as the configuration of the subscriber radios and ID assignment for the individual radios would need to be controlled or it would simply be chaos.  Tier 2 DMR allows for proprietary trunking methods like Capacity Plus from Motorola that will ONLY work from a Motorola radio.  

P25, which I would actually prefer, does NOTHING for increasing bandwidth allocation, unless you went to a Phase 2 APCO25 standard.  But the requirements for that are radios that are thousands of dollars and back end equipment that would be in the tens of thousands.  So that is a pipe dream.  And linking P25 is FAR more complicated than linking analog or DMR.  DMR linking is simple, other than every device on the linked system needs a specifically assigned ID.  Call routing mandates this.  But outside of that, a Motorola repeater that is DMR has an Ethernet jack in the back.  You configure the repeater a certain way, and connect it to the Internet.  There has to be a C-Bridge somewhere as there is a hard limit of 15 repeaters that can be linked together with out the C-Bridge, but outside that, you can route talk groups with the bridge to limit the number of active repeaters by the talk group being used.  Meaning a TG (talkgroup) could exist for each state, region, or a nation wide group simply by routing the TG to the repeaters in the footprint of the TG designated area. 

Any of this would of course interfere with legacy analog equipment and communications in analog.  There would almost certainly need to be some level of restriction of what repeater pairs could be used and how far they would need to be placed apart from current analog repeaters to minimize interference.  DMR talks further, which increases the possibility of analog interference.    And while I am all for it, and the conversion for ME is as simple as going to the tower and reprogramming my repeater (running an MTR3000 on the 462.675 machine) if you look at the coverage footprint of 675 on the map, running an analog repeater in that footprint would be near impossible as my transmitted output would tear the analog receive up for those operators.

So, given the current regulations, and assuming the FCC would change it's mind, what do you think has the best change of getting serious consideration? We have to be realistic here. The FCC isn't likely to make major changes that could have negative impacts on existing users. They made a mess of things previously by allowing the marketing of dual service radios, GMRS/FRS, and tried to clean it up with the 2017 changes. This is the conversion we need to have and have an open mind about it.

[gortex2]

Personally as much as folks want digital I think its in FCC and evey one best interest to stay analog. There are only a handful of repeaters for GMRS and if we add in DMR, P25, NXDN then it will turn into the ham bands. If you really need digital get a ham license or another license and use that service.  

[DONE]

12 minutes ago, Lscott said:

So, given the current regulations, and assuming the FCC would change it's mind, what do you think has the best change of getting serious consideration? We have to be realistic here. The FCC isn't likely to make major changes that could have negative impacts on existing users. They made a mess of things previously by allowing the marketing of dual service radios, GMRS/FRS, and tried to clean it up with the 2017 changes. This is the conversion we need to have and have an open mind about it.

Honestly I think the reasonable move is take some number of the repeater pairs but not all at this time and allow them to be DMR.  Because you're right, the FCC can certainly make a mess of things.  DMR is going to increase the 'available' channels due to the TDMA portion of it.  This CAN'T be applied to the FRS portion because no radios that are DMR can legally be FRS due to power and antenna restrictions.  It would need to be a repeater only sort of thing.  Now is that every other repeater pair, the lower or upper half, or what,,, I have no idea.  I think every other pair starting with 550 and going up, but that's just my opinion.  And no specific requirement to switch should exist.  If an area or group of users has an analog repeater in place and don't see a need to change, then they shouldn't.  But they would need to understand that someone else CAN bring up a digital repeater on their frequency and they would have no grounds to complain about the interference from that repeater. 

What I don't see is any significant benefit for applying digital to simplex channels.  This should be a repeater only effort, and done in a way to minimize the number of people that are going to be negatively effected. 

I will also say that if this happens, the regulations for NOT linking need to go completely away.  There is a sot of gray area that we operate in right now as the regulation specifically states that the switched telephone network can't be used for linking.  We operate the links based on the fact they are IP and not switched telephone circuits.  But much of the telephone system is now IP based and NOT the old two technology that existed when the regulation was written. 

One of the other things with DMR is the ease of standardization of the subscriber configuration.  Meaning that we as repeater owners can mandate that if a user is going to operate on our repeater, they will use specific settings in their radios for microphone gain and such.  This is something the Ham's never really enforced and the reason one guy will boom in and you can barely hear the next guy.  No standardization.  And controlling access to 'private' repeaters is simpler with DMR as well.  Motorola, after suing Hytera started pushing RAC (repeater access control) very hard.  Where before you needed to turn in on in a new repeater, now you have the turn it off.  But this lends it self to controlling access in a repeater system as only folks with permission and the code can access the repeater.  The only negative to that  is the users will need to have a Motorola radio to access the Motorola repeater if RAC is enabled.  But for private groups, that is a small price to pay and second gen (XRP4500 and 6000 series ) radios are getting less expensive on the used market. 

[Lscott]

13 minutes ago, WRKC935 said:

Honestly I think the reasonable move is take some number of the repeater pairs but not all at this time and allow them to be DMR.  Because you're right, the FCC can certainly make a mess of things.  DMR is going to increase the 'available' channels due to the TDMA portion of it.  This CAN'T be applied to the FRS portion because no radios that are DMR can legally be FRS due to power and antenna restrictions.  It would need to be a repeater only sort of thing.  Now is that every other repeater pair, the lower or upper half, or what,,, I have no idea.  I think every other pair starting with 550 and going up, but that's just my opinion.  And no specific requirement to switch should exist.  If an area or group of users has an analog repeater in place and don't see a need to change, then they shouldn't.  But they would need to understand that someone else CAN bring up a digital repeater on their frequency and they would have no grounds to complain about the interference from that repeater.

I wouldn't be concerned about FRS. It's a different service, and effectively unlicensed at that. If an FRS user wants to use digital voice, well let them pay for a license. It's another perk of getting licensed besides using higher power and access to repeater operation.

The repeater idea has merit. I believe that dual mode equipment is available, which will automatically switch between analog and digital modes. 

The negative aspect is too many non-technical GMRS users have trouble figuring out what offsets and tones are judging by the frequent posts on the forum asking for help. Now throw in color codes, slots, talk-groups and user ID's, well even some experienced radio buffs have a bit of a problem with those.

[gortex2]

DMR will only increase the channels if used in TDMA. Rarely that happens. And why should P25 or NXDN be pushed aside for DMR ? That's the issue. Only so many channels for repeaters. And why should an analog user who has had a repeater on the air for 20+ years be interfered with because someone bought a license and put up a DMR repeater in the same area. I know this can happen in Analog also. Still doesn't make it right. Linking should not be part of the digital standard. 

Again I get baffled by trying to make GMRS another ham band. Its one service that has some basic rules that anyone can spend the money on and get a license and use. As said earlier there are many places you can go use DMR, Fusion, P25, and NXDN outside of the GMRS service.