WRAF213 Posted December 7, 2018 Report Share Posted December 7, 2018 P25 voice is not F1D, and F1E is not allowed. Similarly, DMR is not FXD/FXE -- that's a catch-all for different data encapsulations. The FCC has made it very clear that frequency-modulated voice traffic must be F3E or G3E, to prevent manufacturer exclusive voice formats. P25 is not, and for the foreseeable future, will not be allowed on GMRS, just like all other digital voice formats. They express this in the 2017 report on Part 95 reform and 95.1787. Hans 1 Quote Link to comment Share on other sites More sharing options...
Radioguy7268 Posted December 7, 2018 Report Share Posted December 7, 2018 I agree with your comment about Digital emissions, the FCC has been pretty clear that GMRS is supposed to be analog voice in a clear & unencrypted state (foreign languages allowed - as long as your ID is in English or CWID).Asking what's for dinner on a Part 90 system is fine if kept to a minimum; regulators almost certainly won't be pedantic about that. Creating a Part 90 system and inviting a closed group of friends to do casual conversation on it is not. Openly inviting people to join the system for casual conversation will get your license revoked. The FCC can do a station inspection if they suspect this, regardless of whether you're using encrpytion. Whether they end up doing so or not is irrelevant, that doesn't make it any more legal or responsible. However, when it comes to Part 90, I'm pretty sure that an FB6 private carrier repeater license can be used any way that a paying customer chooses to use it. I've never seen a single action from the FCC since the deregulation in 1980 for "casual communication" on Part 90 frequencies. I've got more than one licensed FB6 (and FB8) system, and I've never cared what a customer talked about. I also don't think the FCC ever asked to look at my books and see how much I was charging those FB6 customers. I think the definition of "Private Carrier" is fairly loose. I just told the Frequency Coordinators that I was planning to offer airtime service to my customers. Hans and gortex2 2 Quote Link to comment Share on other sites More sharing options...
MikeSD Posted November 13, 2020 Report Share Posted November 13, 2020 All this appears to be old and out of date data. If it is, these threads need to be closed or flagged. It's giving wrong information. Apparently the FCC has certified some radios for DMR on GMRS. From FCC"In 2017, the FCC updated the GMRS by allotting additional interstitial channels in the 467 MHz band, increased the license term from 5 to 10 years, allowed transmission of limited data applications such as text messaging and GPS location information and made other updates to the GMRS rules to reflect modern application of the service." As far as I know DMR is the only way to send text messages and GPS. And of course, you still have the type 90 vs. 95 but that's another story. And as far as interference, DMR is no more interference that someone walking all over your transmissions, because they can't hear you. Interference will never go away. But DMR has a great possibility to eliminate interference for the most part. And texts are very short interference. And because of the time slot nature, I believe that DMR prevents someone from walking over your conversation, if the radio detects a channel is in use, assuming the other radio is DMR also. I haven't tried this but that's what TDMA does. Please correct me, if I'm wrong. Quote Link to comment Share on other sites More sharing options...
n4gix Posted November 13, 2020 Report Share Posted November 13, 2020 All this appears to be old and out of date data. If it is, these threads need to be closed or flagged. It's giving wrong information. Apparently the FCC has certified some radios for DMR on GMRS. From FCC"In 2017, the FCC updated the GMRS by allotting additional interstitial channels in the 467 MHz band, increased the license term from 5 to 10 years, allowed transmission of limited data applications such as text messaging and GPS location information and made other updates to the GMRS rules to reflect modern application of the service." As far as I know DMR is the only way to send text messages and GPS. And of course, you still have the type 90 vs. 95 but that's another story. DMR is still not allowed. SMS and GPS position are transmitted via analog FM. DMR uses narrow-band versus GMRS remains primarily wide-band. berkinet, Radioguy7268 and Hans 3 Quote Link to comment Share on other sites More sharing options...
MikeSD Posted November 13, 2020 Report Share Posted November 13, 2020 DMR is still not allowed. SMS and GPS position are transmitted via analog FM. DMR uses narrow-band versus GMRS remains primarily wide-band.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. 7. GMRS data applications. The part 95 R&O granted a Petition for Rulemaking filed by Garmin which would allow GMRS handheld portable devices to transmit digital data messages. These messages will be limited to location information, requests for location information from other units, and brief text messages to another specific unit; must be initiated by a manual action or command of a user, except that a unit receiving a location request from another unit may automatically respond with its location; must not exceed one second in duration; and must not be sent more frequently than one digital data transmission within any thirty-second period, excluding automatic responses to location requests. Moreover, GMRS transmitters capable of digital data transmissions: Must have integrated (i.e., non-detachable) antennas; and may make digital data transmissions only on the 462 MHz GMRS channels and the new 467 MHz interstitial GMRS channels shared with the FRS. In addition, the part 95 R&O limited the occupied emission bandwidth of digital data transmissions to 12.5 kilohertz on the 462 MHz and 467 MHz interstitial channels, but allow up to 20 kHz on the 462 MHz main GMRS channels to be consistent with other GMRS emissions that may be using those channels. The Commission concluded the benefits of these new digital message capabilities outweighed the risk of increased interference or congestion in the GMRS. Further, the decision not to permit detachable antennas for GMRS portable units is based upon a concern that an in-line amplifier from a detachable antenna port could allow 467 MHz interstitial operations greatly exceeding the 0.5 Watt power limit and could interfere with repeater operations. Web site: https://www.federalregister.gov/documents/2017/08/29/2017-17395/personal-radio-service-reform Oh, and wideband and narroband is irrelevant in this context. It's very doable to send narrowband transmissions on a wideband system. In fact, it improves interference problems. I could still be wrong, but opinions aren't evidence. If you have something from the FCC that says digital data is not legal, I'm all ears. I do know that digital voice is not allowed at this time (because it violates the 1 sec. every 30 second guideline), but that was not my question. Quote Link to comment Share on other sites More sharing options...
tweiss3 Posted November 13, 2020 Report Share Posted November 13, 2020 95.1771 GMRS emission types.§ 95.1771 GMRS emission types.Each GMRS transmitter type must be designed to satisfy the emission capability rules in this section. Operation of GMRS stations must also be in compliance with these rules.(a) Each GMRS transmitter type must have the capability to transmit F3E or G3E emissions.( Only emission types A1D, F1D, G1D, H1D, J1D, R1D, A3E, F3E, G3E, H3E, J3E, R3E, F2D, and G2D are authorized for use in the GMRS. Equipment for which certification is sought under this subpart may have capabilities to transmit other emission types intended for use in other services, provided that these emission types can be deactivated when the equipment is used in the GMRS. F1E & F2E would possibly permit DMR, however 95.1787 GMRS additional requirements.§ 95.1787 GMRS additional requirements.Each hand-held portable unit transmitter type submitted for certification under this subpart is subject to the rules in this section.(a) Digital data transmissions. GMRS hand-held portable units that have the capability to transmit digital data must be designed to meet the following requirements.(1) Digital data transmissions must only be initiated by a manual action by the operator, except that GMRS units may automatically respond with location data upon receiving an interrogation request from another GMRS or FRS unit.(2) Digital data transmissions must not exceed one second in duration.(3) Digital data transmissions must not be sent more frequently than one digital data transmission within a thirty-second period, except that a GMRS unit may automatically respond to more than one interrogation request received within a thirty-second period.(4) The antenna must be a non-removable integral part of the GMRS unit.(5) GMRS units must not be capable of transmitting digital data on the 467 MHz main channels.( [Reserved] The above requires digital to be performed by an HT with no removable antenna, and it cannot transmit on the repeater input frequencies. This makes DMR impossible unless you are doing DMR simplex. Good luck finding part 95 equipment that can do DMR simplex. The intent was to allow some devices text on FRS HTs, which was a niche thing a little while ago. berkinet and Hans 2 Quote Link to comment Share on other sites More sharing options...
Hans Posted November 13, 2020 Report Share Posted November 13, 2020 AFAIK, it was a carve-out to specifically allow the Garmin Rino line of radios to continue to operate. So far, the FCC has continued to block DMR on GMRS except in a certain instance, IIRC, where someone requested a special license allowance for DMR to do testing/research. Radioguy7268, Elkhunter521, berkinet and 1 other 4 Quote Link to comment Share on other sites More sharing options...
Hans Posted November 13, 2020 Report Share Posted November 13, 2020 The intent was to allow some devices text on FRS HTs, which was a niche thing a little while ago. It still exists... https://buy.garmin.com/en-US/US/c12521-p1.html?series=BRAND476&sorter=featuredProducts-desc Quote Link to comment Share on other sites More sharing options...
MikeSD Posted November 14, 2020 Report Share Posted November 14, 2020 unless you are doing DMR simplex. Good luck finding part 95 equipment that can do DMR simplex.That is exactly my need. Sending short bursts of text messages. My question wasn't about "finding equipment". It was about what is legal and what is not. You and the FCC seems to have said it's legal. Just limited. Finding part 95 equipment is an entirely different subject. But I have found that eventually the FCC comes around to what people use. It used to be illegal to have GMRS handhelds with removable antenna, not now. It used to be illegal to transmit 2W on FRS. Not now. It used to be illegal to transmit high power on CB. Not now. What changed? People used it and the FCC came around. So it's not about finding equipment. It's what's legal and what's not. That was the question. And the reason I asked is because I like to stay on the right side of the line. So knowing exactly where the line is, helps. Thanks for the comments. Quote Link to comment Share on other sites More sharing options...
joeard900 Posted November 14, 2020 Report Share Posted November 14, 2020 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. Quote Link to comment Share on other sites More sharing options...
tweiss3 Posted November 14, 2020 Report Share Posted November 14, 2020 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.The rule is the radio must be Part95. That being said, my Anytime 878UV is a great radio that will operate on the entire UHF spectrum band and is Part90 certified if you keep it in commercial mode. Quote Link to comment Share on other sites More sharing options...
tweiss3 Posted November 14, 2020 Report Share Posted November 14, 2020 That is exactly my need. Sending short bursts of text messages. My question wasn't about "finding equipment". It was about what is legal and what is not. You and the FCC seems to have said it's legal. Just limited. Finding part 95 equipment is an entirely different subject. But I have found that eventually the FCC comes around to what people use. It used to be illegal to have GMRS handhelds with removable antenna, not now. It used to be illegal to transmit 2W on FRS. Not now. It used to be illegal to transmit high power on CB. Not now. What changed? People used it and the FCC came around. So it's not about finding equipment. It's what's legal and what's not. That was the question. And the reason I asked is because I like to stay on the right side of the line. So knowing exactly where the line is, helps. Thanks for the comments.While the emission type is permitted (equipment aside) I honestly don't know if DMR text messages exceed the 1s transmission time limit. If you really want to do GMRS DMR, apply for a variance with the FCC. I know they have granted a few in CA for experimental purposes. I don't know the circumstances, but worth a shot. It does beg a different question, why? You could do a private DMR repeater in amateur radio extremely easily. Hans 1 Quote Link to comment Share on other sites More sharing options...
Hans Posted November 14, 2020 Report Share Posted November 14, 2020 That is exactly my need. Sending short bursts of text messages. My question wasn't about "finding equipment". It was about what is legal and what is not. You and the FCC seems to have said it's legal. Just limited. Finding part 95 equipment is an entirely different subject. But I have found that eventually the FCC comes around to what people use. It used to be illegal to have GMRS handhelds with removable antenna, not now. It used to be illegal to transmit 2W on FRS. Not now. It used to be illegal to transmit high power on CB. Not now. What changed? People used it and the FCC came around. So it's not about finding equipment. It's what's legal and what's not. That was the question. And the reason I asked is because I like to stay on the right side of the line. So knowing exactly where the line is, helps. Thanks for the comments."You and the FCC seems to have said it's legal. Just limited" No, the FCC has stated that DMR is not acceptable on GMRS at this time. The only allowance they made was for FRS and only in the finite definitions of when and how in part 95. "It used to be illegal to have GMRS handhelds with removable antenna, not now." AFAIK, it was not illegal to have GMRS handhelds with removable antennae. That was FRS. The reason you saw that with the FRS/GMRS combination handhelds was to comply with FRS. Now, of course, no more dual use handhelds can be marketed under the rules. "It used to be illegal to transmit high power on CB. Not now." No, the current rules still limit CB to 4 watts AM and 12 watts SSB. "So knowing exactly where the line is, helps." You need to look carefully at part 95 yourself and then ask questions. It is written in plain English. https://www.law.cornell.edu/cfr/text/47/part-95 Radioguy7268 and berkinet 2 Quote Link to comment Share on other sites More sharing options...
Hans Posted November 14, 2020 Report Share Posted November 14, 2020 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. The frequencies are just frequencies. Of course, DMR works perfectly fine on GMRS frequencies! There are even parts of the country where you can find DMR, P25, etc repeaters on GMRS. There have been several radio operators in my AO using DMR on simplex regularly. However, part 95 does not currently allow it and the FCC has been quite resistant to the idea. Quote Link to comment Share on other sites More sharing options...
Hans Posted November 14, 2020 Report Share Posted November 14, 2020 While the emission type is permitted (equipment aside) I honestly don't know if DMR text messages exceed the 1s transmission time limit. If you really want to do GMRS DMR, apply for a variance with the FCC. I know they have granted a few in CA for experimental purposes. I don't know the circumstances, but worth a shot. It does beg a different question, why? You could do a private DMR repeater in amateur radio extremely easily. 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. Quote Link to comment Share on other sites More sharing options...
MikeSD Posted November 14, 2020 Report Share Posted November 14, 2020 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 1 Quote Link to comment Share on other sites More sharing options...
n4gix Posted November 14, 2020 Report Share Posted November 14, 2020 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. Motorola XPR7550 UHF Anytone 868UV Ailunce HD-1 (U/V) Radioddity GD-77 (U/V) TYT MD-2017 Motorola XPR5550 UHF 2x Connect Systems CS800 UHF Connect Systems CS800D U/V joeard900 and Hans 2 Quote Link to comment Share on other sites More sharing options...
n4gix Posted November 14, 2020 Report Share Posted November 14, 2020 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 2 Quote Link to comment Share on other sites More sharing options...
Hans Posted November 15, 2020 Report Share Posted November 15, 2020 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. gortex2 1 Quote Link to comment Share on other sites More sharing options...
Lscott Posted November 15, 2020 Report Share Posted November 15, 2020 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.com/blog/What%27s-Single-frequency-repeater-function https://www.rexontec.com.tw/en/product/RPT-810.html Hans 1 Quote Link to comment Share on other sites More sharing options...
gman1971 Posted November 16, 2020 Report Share Posted November 16, 2020 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.com/blog/What%27s-Single-frequency-repeater-function https://www.rexontec.com.tw/en/product/RPT-810.html Quote Link to comment Share on other sites More sharing options...
Lscott Posted November 16, 2020 Report Share Posted November 16, 2020 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. Quote Link to comment Share on other sites More sharing options...
gman1971 Posted November 16, 2020 Report Share Posted November 16, 2020 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. Quote Link to comment Share on other sites More sharing options...
Lscott Posted November 16, 2020 Report Share Posted November 16, 2020 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 1 Quote Link to comment Share on other sites More sharing options...
WRFP517 Posted December 14, 2020 Report Share Posted December 14, 2020 when are we going to be able to go to DMR on the GMRS Service i would love it to see us able to use DMR on the gmrs System and 1 big reason is it unlawful to use the internet for GMRS period or to have gmrs connected to telephone or computers system while active so that sums it up .... but that like the FCC rules state all thats all ID ing must must be done with english simple languge or cw but i hear alot of different languges doing there ID on gmrs and amatuer so i guess theat rule doesnt count lol just saying Quote Link to comment Share on other sites More sharing options...
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