Jump to content

BuyTwoWayRadios.com

Photo

DMR on GMRS

DMR on GMRS

  • Please log in to reply
48 replies to this topic

#41 MikeSD

MikeSD

    Newbie

  • Members
  • Pip
  • 7 posts
  • LocationWA State
  • GMRS Callsign:WRJU663
  • Ham Callsign:KC7VE

Posted 14 November 2020 - 12:34 PM

 
I think I can answer that... Some, like me, don't want the hassle of frequency coordination and prefer the broader use allowed by GMRS. As I understand it in my AO, frequency coordination has locked up most amateur radio repeater pairs. Some are camped on the pairs without even having a repeater on the air for years/decades. When I checked into it some time back, I was told "Good luck getting a pair!" by local hamsters.
 
We also use GMRS for actual work; can't do that with amateur. Additionally, there is the big appeal of immediate family members being able to transmit under the one license; no tests required.

 

Frequency coordination is not really official. They really have no power to stop anyone from doing anything.  All the FCC cares about is interference between users. FACT, if someone has a parked frequency pair, for amateur radio, but it's not used, and you put up a repeater, the FCC will not give a damn.  If there is no interference, there is no problem.  frequency coordinators do not own the frequencies. If they file a complaint with the FCC and there is no interference, the FCC won't care.

 

To the person who wondered if DMR will work on GMRS, of course it works just fine.  In fact, if DMR is ever adopted, it will greatly expand the use of GMRS.  But FCC is always making sure that changes are backward compatible.  Fact is DMR would reduce a lot of interference.  That's what it's designed to do, and you get double the capacity, if not more. Two conversations can take place simultaneously on the same frequencies.

 

Regarding how long it takes to transmit a text. This example is "I'll be headed home soon".  It was transmitted in DMR message, into a dummy load, and i real time speed.  You can hear the beep, when the message was sent.

 

msdsite.com/DMR/dmr.mp3

 

But being legal is an entirely different matter.


  • wqhk941 likes this

--

USMC, 1963-1967

Ham: KC7VE

GMRS: WRJU663


#42 n4gix

n4gix

    Advanced Member

  • Members
  • PipPipPip
  • 634 posts
  • GMRS Callsign:WQWU626
  • Ham Callsign:N4GIX

Posted 14 November 2020 - 05:51 PM

I have been following this thread for a little bit now, a lot of really good information! Has anyone that uses a DMR radio in the HAM world programmed it to work in analog on the GMRS frequencies? I am thinking about getting into the DMR world on the ham side and would love to be able to have the GMRS freqs in there just in case. 

I have five DMR HT's from various manufacturers all of which work analog GMRS just fine. I also have four mobile DMR transceivers that will do analog GMRS as well as the intended amateur DMR VHF and UHF.

 

  1. Motorola XPR7550 UHF
  2. Anytone 868UV
  3. Ailunce HD-1 (U/V)
  4. Radioddity GD-77 (U/V)
  5. TYT MD-2017
  1. Motorola XPR5550 UHF
  2. 2x Connect Systems CS800 UHF
  3. Connect Systems CS800D U/V

  • Hans and WRJK209 like this

#43 n4gix

n4gix

    Advanced Member

  • Members
  • PipPipPip
  • 634 posts
  • GMRS Callsign:WQWU626
  • Ham Callsign:N4GIX

Posted 14 November 2020 - 05:54 PM

I think I'll take exception to that.  Can you show the rule that prohibits it?  I can show you a federal.gov site that says "digital" data transmissions is allowedd on GMRS.

You first made a claim that DMR is permitted on GMRS frequencies. The answer is still no, it is not permitted.

 

Some limited form of digital data is allowed however, that much is accurate.

 

Of course DMR will work on GMRS frequencies, but it is not legal. I agree that it would be nice, but not practical because of the sheer number of legacy analog systems already in use.


  • Hans and Radioguy7268 like this

#44 Hans

Hans

    Advanced Member

  • Members
  • PipPipPip
  • 351 posts
  • LocationTrapped in Yankee territory
  • GMRS Callsign:WQXE920
  • Ham Callsign:N8VHF

Posted 14 November 2020 - 07:52 PM

Frequency coordination is not really official. They really have no power to stop anyone from doing anything.  All the FCC cares about is interference between users. FACT, if someone has a parked frequency pair, for amateur radio, but it's not used, and you put up a repeater, the FCC will not give a damn.  If there is no interference, there is no problem.  frequency coordinators do not own the frequencies. If they file a complaint with the FCC and there is no interference, the FCC won't care.

 
Yep, I am aware. However, it was made perfectly clear by local hamsters that the ostracization and the intentional QRM that would follow on any amateur repeater that I put up without coordination would make it annoying and mostly unused and unusable. It's like that in my AO. Then, there is the limitation on work traffic and the individual license factor for family members and friends' families. GMRS solves all of those problems for us here.


  • kb2ztx likes this

#45 Lscott

Lscott

    Advanced Member

  • Members
  • PipPipPip
  • 307 posts
  • GMRS Callsign:WRBZ532
  • Ham Callsign:KC8LDO

Posted 15 November 2020 - 01:52 AM

 

 That's what it's designed to do, and you get double the capacity, if not more. Two conversations can take place simultaneously on the same frequencies.

 

I believe that is only true when operating through a DMR repeater. The repeater supplies the sync signal so each radio knows when to transmit based on the time slot selected.

 

When operating simplex there is no sync signal to determine which of the two times slots is slot 1 or slot 2. 

 

One of the interesting aspects of DMR is with the right programming of the firmware a radio could supply the sync signal. In the case of the D578UV, from what I've read, can do this thus you can run a single frequency repeater, no offset or tuned cavity filters required. There are some other DMR radios that claim to have the feature as well.

 

https://www.ailunce....peater-function

 

https://www.rexontec...ct/RPT-810.html


  • Hans likes this

#46 gman1971

gman1971

    Advanced Member

  • Members
  • PipPipPip
  • 368 posts
  • LocationWisconsin

Posted 16 November 2020 - 07:02 AM

Not quite...

 

DMR offers DCDM, which translates to: Dual Capacity Direct Mode, which allows for simplex two time slot operation without a repeater, as in: YES, you can have two conversations on the same channel without a repeater. The radios select a timing leader among the eligible radios, and you can also hint to have one as leader, etc... all when in DCDM mode.  It works great, but it doesn't work very well on CCRs... as I've tried a bunch of them, and DCDM usually hangs the radios on most of the POS TYT's I've tried... Now, it works great on my EVX mobiles and portables, and of course it works great on the XPR gen2 radios too... (the 6550 doesn't have DCDM)

 

If you want DMR with properly functioning DCDM you need to get something along the lines of an XPR7550, preferably an e model, just don't waste your money on Aliunce, Rexontec... et. all... CCR garbage... 

 

As for the Anytone AT-578... yeah, it has an SFR alright?, but its a piece of garbage: It freezes while operating in Single Frequency Repeater all the time. I have one, I've had one for almost a year now, its a dead weight piece of trash that will hang when you need it the most... its useless. Mine collecting dust in the parts bin...  and yes, its been upgraded to latest FW, latest baseband etc. etc... still a piece of trash that will hang and freeze up. Again, if you want a real Single Frequency Repeater that won't check out when you might need it the most you're ( and I am ) gonna have to muster up for the SLR1000 Moto repeater, a 2 grand wonder... nothing else made in China will touch that thing... that is if long range and good reliability are your thing... otherwise, be prepared to deal with maintenance and upkeep when these CCR turds stop working... or when range is measured in tenths of a mile, rather than tens of miles, etc... yup... If you want professional results you need to buy professional equipment, how do I make such assessment? Well, I found this the hard way, after sinking a lot of money on garbage radios...  stay away...

 

but if you must, buy CCRs at your own peril, just don't expect miracles...

 

G.

 

 

 

I believe that is only true when operating through a DMR repeater. The repeater supplies the sync signal so each radio knows when to transmit based on the time slot selected.

 

When operating simplex there is no sync signal to determine which of the two times slots is slot 1 or slot 2. 

 

One of the interesting aspects of DMR is with the right programming of the firmware a radio could supply the sync signal. In the case of the D578UV, from what I've read, can do this thus you can run a single frequency repeater, no offset or tuned cavity filters required. There are some other DMR radios that claim to have the feature as well.

 

https://www.ailunce....peater-function

 

https://www.rexontec...ct/RPT-810.html



#47 Lscott

Lscott

    Advanced Member

  • Members
  • PipPipPip
  • 307 posts
  • GMRS Callsign:WRBZ532
  • Ham Callsign:KC8LDO

Posted 16 November 2020 - 08:48 AM

Not quite...

 

DMR offers DCDM, which translates to: Dual Capacity Direct Mode, which allows for simplex two time slot operation without a repeater, as in: YES, you can have two conversations on the same channel without a repeater. The radios select a timing leader among the eligible radios, and you can also hint to have one as leader, etc... all when in DCDM mode.  It works great, but it doesn't work very well on CCRs... as I've tried a bunch of them, and DCDM usually hangs the radios on most of the POS TYT's I've tried... Now, it works great on my EVX mobiles and portables, and of course it works great on the XPR gen2 radios too... (the 6550 doesn't have DCDM)

 

If you want DMR with properly functioning DCDM you need to get something along the lines of an XPR7550, preferably an e model, just don't waste your money on Aliunce, Rexontec... et. all... CCR garbage... 

 

As for the Anytone AT-578... yeah, it has an SFR alright?, but its a piece of garbage: It freezes while operating in Single Frequency Repeater all the time. I have one, I've had one for almost a year now, its a dead weight piece of trash that will hang when you need it the most... its useless. Mine collecting dust in the parts bin...  and yes, its been upgraded to latest FW, latest baseband etc. etc... still a piece of trash that will hang and freeze up. Again, if you want a real Single Frequency Repeater that won't check out when you might need it the most you're ( and I am ) gonna have to muster up for the SLR1000 Moto repeater, a 2 grand wonder... nothing else made in China will touch that thing... that is if long range and good reliability are your thing... otherwise, be prepared to deal with maintenance and upkeep when these CCR turds stop working... or when range is measured in tenths of a mile, rather than tens of miles, etc... yup... If you want professional results you need to buy professional equipment, how do I make such assessment? Well, I found this the hard way, after sinking a lot of money on garbage radios...  stay away...

 

but if you must, buy CCRs at your own peril, just don't expect miracles...

 

G.

DCDM, allows two voice channels on the same frequency. That's good to know. I wasn't aware there are radios that could coordinate the time slot sharing without a repeater in the mix. The question there is how many DMR radios have that capacity?

 

The point about single frequency repeaters using DMR I think is a significant development. It just so happens the CCR's I linked to offer it but I'm not advocating people buy those CCR's, just used them as an example.



#48 gman1971

gman1971

    Advanced Member

  • Members
  • PipPipPip
  • 368 posts
  • LocationWisconsin

Posted 16 November 2020 - 01:34 PM

Yeah, DCDM is awesome, and ERDM is even more awesome, IMO, of course... :)

 

Totally agree with you on SFRs... 

 

You can also make your own SFR (Single Frequency Repeater) with two radios operating in DCDM mode and a circular isolator (tuned to the frequency you want) Enable both radios as DCDM mode, then have one of the radios set as RX only for TS 1, make this radio ineligible for timing leader, and the other radio set normally but to TX on TS 2, make this radio preferred timing leader too. On your subscriber Gen2 XPR7550/SL7550, etc... radios you enable ERDM, which will listen to whatever time slot has the strongest incoming signal... so you get automatic talkaround switching for "free", as in: your radio will either listen directly to the TXing radio, talking on TS 1, or if the TS1 signal is too weak, or not there at all, it will automatically use the TS2 signal coming from the SFR. Can't beat that...  

 

The circular isolator can be replaced with a solid state T/R switch... but I yet have to find one of those switches that isn't worth an arm and a leg... mechanical T/R switches won't work, a relay won't last very long switching at DMR TDMA rates... 

 

G.

 

 

DCDM, allows two voice channels on the same frequency. That's good to know. I wasn't aware there are radios that could coordinate the time slot sharing without a repeater in the mix. The question there is how many DMR radios have that capacity?

 

The point about single frequency repeaters using DMR I think is a significant development. It just so happens the CCR's I linked to offer it but I'm not advocating people buy those CCR's, just used them as an example.



#49 Lscott

Lscott

    Advanced Member

  • Members
  • PipPipPip
  • 307 posts
  • GMRS Callsign:WRBZ532
  • Ham Callsign:KC8LDO

Posted 16 November 2020 - 03:41 PM

Yeah, DCDM is awesome, and ERDM is even more awesome, IMO, of course... :)

 

Totally agree with you on SFRs... 

 

You can also make your own SFR (Single Frequency Repeater) with two radios operating in DCDM mode and a circular isolator (tuned to the frequency you want) Enable both radios as DCDM mode, then have one of the radios set as RX only for TS 1, make this radio ineligible for timing leader, and the other radio set normally but to TX on TS 2, make this radio preferred timing leader too. On your subscriber Gen2 XPR7550/SL7550, etc... radios you enable ERDM, which will listen to whatever time slot has the strongest incoming signal... so you get automatic talkaround switching for "free", as in: your radio will either listen directly to the TXing radio, talking on TS 1, or if the TS1 signal is too weak, or not there at all, it will automatically use the TS2 signal coming from the SFR. Can't beat that...  

 

The circular isolator can be replaced with a solid state T/R switch... but I yet have to find one of those switches that isn't worth an arm and a leg... mechanical T/R switches won't work, a relay won't last very long switching at DMR TDMA rates... 

 

G.

If GMRS ever allows DMR I would think SFR mode would be the way to go since it would be simple for a user to setup, no fancy controller or cavity filters to deal with.

 

In fact this would be ideal for a Ham buddy that's into off-roading with his Jeep and the group he belongs to. They are switching to GMRS since that seems to be the direction the off-roading community is moving towards. He's trying to get the group members to get their Ham Tech class tickets. If he can do that then using DMR with one radio setup as the repeater using SFR mode would fit exactly what they are looking for without a complex system to drag around. If a particular frequency is busy you just switch to another one. Can't do that in the field with a conventional setup.


  • gman1971 likes this




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users