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DMR on GMRS


parighttobeararms
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GMRS can be linked via internet, there are entire GMRS networks already in place... now you're saying its illegal? 

 

G.

 

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 

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GMRS can be linked via internet, there are entire GMRS networks already in place... now you're saying its illegal? 

 

G.

 

according to FCC we cant use internet with GMRS .... but yes there are alot of people doing alot of things on gmrs doesnt mean there suppose to be doing it lol .....what ive noticed is alot of people read the fcc ruls and regs and just comply to the ones that they want to and disregard the ones they dont like lol just my observation ... just like the rule stating ID ing must be done in simple english lol 

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what ive noticed is alot of people read the fcc ruls and regs and just comply to the ones that they want to and disregard the ones they dont like lol just my observation ... just like the rule stating ID ing must be done in simple english lol 

 

I'll agree that plenty of people pick and choose the rules they like & disregard those they don't. I was wondering about  your comment regarding the ID requirements (Around here, I always hear people ID'ing in English - even if they're speaking another language during their conversation) - but then I saw that you're in Puerto Rico. I'd guess there's a little bit of a special case there. I'd have serious doubts that the FCC would ever get around to trying to enforce that rule on the "isla del encanto".

 

Add me to the list of those who would like to see the exact rule that prohibits Internet linking. I'm of the understanding that they're doing a bunch of linking down in Puerto Rico ever since Hurricane Maria.

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For clarity. Morse code is permitted for station identification on GMRS. The below text is copied verbatim from 2017 (current) version of the rules.

 

95.1751 paragraph ‘b’ “The call sign must be transmitted using voice in the English language or international Morse code telegraphy using an audible tone.”

 

Michael

WRHS965

KE8PLM

 

... just like the rule stating ID ing must be done in simple english...

Sent from my iPad using Tapatalk

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In 95.345, .347 and .349 of part 95 rules disallow remote control, automatic control and network connection for all services, unless expressly allowed for it within the sub-part text for that service. The following is extracted directly from the sub part 95E text for GMRS.

 

§ 95.1745 GMRS remote control.

 

Notwithstanding the prohibition in § 95.345, GMRS repeater, base and fixed stations may be operated by remote control.

 

§ 95.1747 GMRS automatic control.

 

Notwithstanding the prohibition in § 95.347, GMRS repeater stations may be operated by automatic control.

 

§ 95.1749 GMRS network connection.

 

Operation of a GMRS station with a telephone connection is prohibited, as in § 95.349. GMRS repeater, base and fixed stations, however, may be connected to the public switched network or other networks for the sole purpose of operation by remote control pursuant to § 95.1745

 

Hope this helps.

 

Michael

WRHS965

KE8PLM

 

 

Sent from my iPad using Tapatalk

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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.

 

 

DMR SFR mode would ideal for locations with no other co-located repeaters, such as at home or at non-commercial radio sites.   And most seem to work with any manufacturers's handheld or vehicle radios.   I had considered using Motorola's outdoor repeater (SLR1000) - see:

 

https://www.motorolasolutions.com/en_us/products/mototrbo-systems/infrastructure/slr-1000.html#tabproductinfo

 

This is the only Moto model capable of SFR.  I considered this at commercial repeater sites as it mounts outdoors on the roof or tower, and connects to a wall-mounted power supply, eliminating the need for an indoor equipment rack (saving money).  You an use one or two antennas.

 

If its a commercial site with combiners, you should likely run separate TX and RX antennas to prevent interference to/from other co-located repeaters transmitting on the low side and receiving on the high side of the channel pairs.   But then you likely need bandpass filters, and internal models are not yet available unless you hang them externally on the tower and liberally apply a gallon of RTV.     

 

Using a single antenna may also cause issues at combined sites or highly-congested ones.  But its 2020, and fewer UHF repeaters actually exist at these sites. 

 

Prices:

Repeater (street new): $1400

Antenna switch: $300

SFP option: $600

 

Not including antennas and line.   

 

Greg

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The SLR 1000 already has the antenna switch.

 

All SLR repeaters can do SFR, but they need the solid state PIN diode switch to work. You can't use a circulator, its been tried.

 

G.

 

DMR SFR mode would ideal for locations with no other co-located repeaters, such as at home or at non-commercial radio sites.   And most seem to work with any manufacturers's handheld or vehicle radios.   I had considered using Motorola's outdoor repeater (SLR1000) - see:

 

https://www.motorolasolutions.com/en_us/products/mototrbo-systems/infrastructure/slr-1000.html#tabproductinfo

 

This is the only Moto model capable of SFR.  I considered this at commercial repeater sites as it mounts outdoors on the roof or tower, and connects to a wall-mounted power supply, eliminating the need for an indoor equipment rack (saving money).  You an use one or two antennas.

 

If its a commercial site with combiners, you should likely run separate TX and RX antennas to prevent interference to/from other co-located repeaters transmitting on the low side and receiving on the high side of the channel pairs.   But then you likely need bandpass filters, and internal models are not yet available unless you hang them externally on the tower and liberally apply a gallon of RTV.     

 

Using a single antenna may also cause issues at combined sites or highly-congested ones.  But its 2020, and fewer UHF repeaters actually exist at these sites. 

 

Prices:

Repeater (street new): $1400

Antenna switch: $300

SFP option: $600

 

Not including antennas and line.   

 

Greg

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I read this on internet - so it must have been true:

 

https://cwh050.blogspot.com/2017/01/extended-range-direct-mode.html

 

______________

 

 

Postscript 04.03.17

A Circulator cannot be used as it does not offer sufficient isolation (<30dB).

- Thanks to Jim for trying this out. Even a negative result is a result. 



Postscript 30.05.18

The SLR1000 has an optional built-in high speed antenna switch that will allow the repeater to be used with a single antenna. The same could be said about the other repeaters but Motorola doesn't produce an antenna switch for them unfortunately.

The antenna relay cannot be used as this is an electro-mechanical device that cannot cope with the high speed switching.

 

______________

 

Does this switch come standard now, or possibly this info is outdated.

 

They mention the isolator approach - I am guessing this is an internal isolator from Moto?  If they get a dual-isolator this will give them 60 dB+, which should be enough.  But the switch may be lower cost.  

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Well, what do you want me to say? Wayne seems to know a lot more than I do, and someone he trusts has tried it, and I have not... so I am going trust their opinion on this one, rather than sow doubt... but you are welcome to try it if you think the "b/c I saw it on the internet, it must be true" mantra...

 

If I understand correctly how isolators work, then I don't think so, the two port Isolators won't work, b/c only whatever signal spills over the first circulator goes onto the 2nd one, so you'll have a 30dB attenuation at the 2nd circulator dummy load (which is where you'll place the receiver radio). You need a switch, unfortunately. 

 

The two SLR1000s I've looked at had the switches installed already, so perhaps it is my assumption that the switch comes standard....  

 

G.

 

 

I read this on internet - so it must have been true:

 

https://cwh050.blogspot.com/2017/01/extended-range-direct-mode.html

 

______________

 

 

Postscript 04.03.17

A Circulator cannot be used as it does not offer sufficient isolation (<30dB).

- Thanks to Jim for trying this out. Even a negative result is a result. 



Postscript 30.05.18

The SLR1000 has an optional built-in high speed antenna switch that will allow the repeater to be used with a single antenna. The same could be said about the other repeaters but Motorola doesn't produce an antenna switch for them unfortunately.

The antenna relay cannot be used as this is an electro-mechanical device that cannot cope with the high speed switching.

 

______________

 

Does this switch come standard now, or possibly this info is outdated.

 

They mention the isolator approach - I am guessing this is an internal isolator from Moto?  If they get a dual-isolator this will give them 60 dB+, which should be enough.  But the switch may be lower cost.  

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Jeez...just making a joke on the internet comment......

 

I have no interest in proving anyone wrong - just providing what someone else noted.  

 

I was incorrect on the isolator as you noted-  as the RX goes on the (load) port closest to the antenna.  So even onmy flawed dual isolator solution, 30 dB is all you get. 

 

(A side note -  this arrangement might also damage the receiver if the antenna VSWR sucked....).

 

G  

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My fault then, I didn't pick it as a joke... I am sorry.

 

G.

 

Jeez...just making a joke on the internet comment......

 

I have no interest in proving anyone wrong - just providing what someone else noted.  

 

I was incorrect on the isolator as you noted-  as the RX goes on the (load) port closest to the antenna.  So even onmy flawed dual isolator solution, 30 dB is all you get. 

 

(A side note -  this arrangement might also damage the receiver if the antenna VSWR sucked....).

 

G  

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First off, I HATE that this is my first post on here.  I would much rather it been the HI. I'm Keith and I'm a radioholic.  I can say that due to getting the bug at the age of about 8 or 10 with CB.

Been an ham for over 20 years and a commercial radio tech for over 10 years.

 

Enough with the introduction.

While I can see the draw to doing DMR on GMRS, I will give a friendly warning about getting what you wish for.

I mentioned the commercial radio tech thing.  And I will comment a bit on first hand experience with DMR and analog on the same frequencies.

First off is DMR modulation causes the signal to carry for distances that are surprising. 

 

We have two customers that are 4 counties away.  Both were analog at one point and they never once had interference issues with each other yet they happened to share 2 frequencies.

One was a 5 site analog simulcast system.  Meaning 5 radio towers in different areas of the county, linked together and transmitting at the same time on the same frequency.

Other customer had 4 different repeater sites and 4 different frequencies.  So then it was decided that the second customer with 4 repeater sites needed to be DMR IP Site connect ( the technology that the ham radio DMR systems are linked with.  And it was not  EVER right, and they were BOTH interfering with each other, immediately.  The DMR was breaking into the analog audio for the analog user, so they were hearing the DMR in places.  And the fact that there was signal from the analog getting into the DMR radios for customer B... they would just hear nothing. 

 

So here's my point.

We have 8 repeater pairs to work with nation wide.  Customer B's DMR repeater that was interfering with Customer A was a 3 db gain antenna on a roof top that was MAYBE 60 feet in the air with a 40 watt radio that was cut back to 20 watts.

Customer A's simulcast system was installed with the antennas below 120 feet to purposely reduce the coverage of the sites because by design you don't want a lot of overlap in an analog simulcast radio system.

Switching from analog to DMR as far as the heard signal, at 50 watts, would be like an analog signal at 300 watts.  And that pulsing type of modulation, busts right through the noise floor and is heard by analog receivers very well, and better than the analog signal. 

So be careful what you wish for.  When this happens, and it probably will at some point.  The repeater that you sometimes hear two counties over, will be busting into your analog radio when you get into the fringe of your repeater coverage area and REDUCE your effective coverage area by as much as a third, with NOTHING that can be done about it. I was told that the FCC even considered reducing the power levels for repeaters in the public safety bands to 10 watts or less for DMR users. 

For those of you that are in the business.  The company I work for is the one that bought BACK a DMR radio system (Customer B's).  That fact is pretty well known in the commercial radio community.  And if you have heard about it, please refrain from mentioning who I work for or the customers out of respect. 

 

I personally would never even consider running a DMR repeater on GMRS unless it was a collaborative effort and it was only on one frequency. And that it was FREE to assess for all GMRS license holders.  Don't get me wrong.  DMR is great.  It would bring in TDMA to GMRS and give license holders twice as many talk paths as we have.  Simplify linking and create the ability to have Group Call's (talk groups... I know,,, I do the Motorola thing).  But the fact that it would create a ton of harmful interference for those folks that are just wanting to do the analog thing.  And enjoy the license and its benefits without needing to completely replace their radio systems,  I can't in good conscience advocate for the change.

 

Just my two cents.

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Good post about DMR issues when mixed with analog on the same or adjacent channels. The two systems don't play together at all. Public safety went through some great pains when MotoTurbo was introduced. It ended up causing a freeze on the four coordinating authorities approving digital license modifications until guidelines could be worked out involving the coordinators and Moto on what would work and what changes to allowable signal levels could be determined.

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Dreaming is always for free, however... I don't think anyone was planning on running a DMR repeater on GMRS on this thread...  and certainly not me. I can see some people running low power simplex DMR, given the vast amount of CCR DMR radios flooding the market its impossible to say nobody will do it... I've already heard DMR on GMRS around here... does it make it right? certainly not. But instead of punitive approaches to the laws, we should perhaps look for incentive approaches to follow the laws... and incentive I don't mean a 5.56 on the other side...

 

JMO.

 

G.

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Digital over FM, on the same exact channel is going to cause problems, not two ways about that. The other way around it doesn't do much, since all it does is increase the Bit Error Rate (BER)... so you might hear a bit of degraded voice... but not much.

 

However, interference is also caused by piss poor transmitters, like those found on CCRs. If you look on another thread you'll see the massive amount of noise those things put out on the harmonics, if you boost that to 50W, then you can see a pretty clear picture... again. You could probably build a coexisting FM/DMR channel setup with high end gear and be less affected than using 29.95 CCR special garbage...  which is what most people are trying to use to implement their repeaters.

 

And to reiterate, and before proceeding any further, DMR is not lawful to use on GMRS... 

 

So, while DMR 12.5kHz might not be the ideal bandwidth to do this with, the Kenwood NXDN on 6.25kHz might work a bit better, always depending on the quality of the radio reciver/transmitter. With that said, you could park your digital frequency the furthest away from the center, and within the channel. On NXDN you'll park 6.25 kHz from the channel's edge (not from the center), leaving plenty of room on the center channel for FM to work pretty much clear of issues. I do know for a fact (tested) that none of my XPR Gen2 radios even blink, while on FM, when there is another XPR portable is blasting @ 5W, 3 feet away, while parked on the edge of their wideband channel (Effectively making it two Narrowband channels out of a Wideband one) But..., of course, the big CAVEAT is that you can't make this work with the typical garbage CCRs et all currently flooding the market, b/c those things don't have the sufficient adjacent channel selectivity, filtering, front end, etc, to pull this off, as tested. That is not counting with the fact that the transmitters are dirty of spurious harmonics and spewing noise all over the bands too.... 

 

G.

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...The company I work for is the one that bought BACK a DMR radio system (Customer B's).  

 

That would have been a great opportunity to do the opposite: sell the analog user a new digital system :)   Digital technology has a lower C/I requirement than analog and would have reduced the effects of the interference from the other system (but maybe not enough).  

 

But seriously, the company did the right thing if they could not use directional antennas to reduce the issues (sometime this is a mobile uplink issue making it more difficult to resolve).

 

Greg      

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"First off is DMR modulation causes the signal to carry for distances that are surprising. "

 

"Switching from analog to DMR as far as the heard signal, at 50 watts, would be like an analog signal at 300 watts.  And that pulsing type of modulation, busts right through the noise floor and is heard by analog receivers very well, and better than the analog signal."

 

 

While physics shows that the signal strength from DMR will be exactly the same at the same distance, I think you mean analog is more susceptible to interference, and DMR is a bit more noticeable even when compared to P25 Phase I or NXDN.  

 

Another major contributing factor is a DMR repeater's duty-cycle.  Repeater duty cycles can be greater because they support two analog channels worth of radio traffic (Slot 1 and Slot 2).  In addition, the primary manufacturer's default hang time is 6 seconds to ensure that field radios are synced up with the repeater slot, particularly for reply messages (otherwise access times increase).  And, since many DMR radios have a direct IP connection (through USB) and built-in GPS, running data application and vehicle location applications further increase to the duty cycle.

 

Add to this analog narrow-banding.  Narrow-banding increased analog FM's susceptibility to co-channel interference by 6 dB, while also reducing effective range by about 3 dB  (which may explain your 50W>>300W affect).  GMRS remains wide-band so it will have less impact.        

 

I don't know if the FCC ever considered a DMR power reduction, but the frequency coordinators did about 5 or 10 years ago.  One system we went to license was hit with an automatic 50% power reduction before they would approve it.  Listening to UHF commercial spectrum, it seems there are significantly more DMR systems than analog in the metro areas (maybe just because of the DMR duty-cycle??).   At least three to one here. 

 

Its just a cost-benefit issue; DMR allows two separate families or groups to use one repeater at the same time - in half the spectrum; a 100% capacity increase).  We only have eight GMRS repeater channels today - so with DMR, fewer repeaters need to be built, creating less GMRS congestion overall.  And it reduced all of the user's initial and recurring costs 50% as they could now be split among twice as many users now.  

 

Once two adjacent channels in an area convert to DMR, you can then (after a minor FCC rule change) run DMR repeaters on the interstitial channels without interference between them - quadrupling use of the band overall.   

 

And digital users get texting, private calling and greater voice clarity.....

 

 

Greg

Add to this analog narrowbanding.  Narrowbanding increased analog FM's susceptibility to co-channel interference by 6 dB (which partially explain your 50W>>300W affect).  GMRS remains wideband so it will have less of an imp

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"...So then it was decided that the second customer with 4 repeater sites needed to be DMR IP Site connect ( the technology that the ham radio DMR systems are linked with...."

 

"Simplify linking and create the ability to have Group Call's (talk groups... I know,,, I do the Motorola thing). "

 

As we only have eight shared channels, the linking would need to be tightly controlled.  We are already seeing one conversation tying up 2-3 channels today over a wide area - and the repeaters don't even monitor for other active co-channel repeaters before activating right on top of them.  Really poor practice.   

 

We have local mountains rising to 4,000 ft. here, so its only appropriate to tie one high-elevation system to really low-elevation ones (like local residential repeaters or hot-spots).

 

Or to be more drastic about it - additional repeaters should not be linked to extend coverage, only to fill gaps in existing coverage (e.g, fill-in areas that would have been otherwise covered, if not for terrain blockage and/or buildings).  FCC tables of range have existed since the 1950's and are still in use today to estimate this based on repeater elevation and power.  Just jam it in Part 95 with a simple math equation.   

 

G  

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Once two adjacent channels in an area convert to DMR, you can then (after a minor FCC rule change) run DMR repeaters on the interstitial channels without interference between them - quadrupling use of the band overall.   

 

What would intrigues me about DMR are some of the radios that will function in SFR, single frequency repeater, mode. Of course you have to find one that works.

 

Anyway the attraction is no requirement for using any kind of "cavity" filters which would be necessary on a more traditional in-band system. This means almost anybody could setup a repeater with far less technical expertise required and cost for a decent set of BPBR filters. So until the FCC changes the rules we won't have DMR on GMRS. I do expect that to happen sooner or later, likely much later.    

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What would intrigues me about DMR are some of the radios that will function in SFR, single frequency repeater, mode. Of course you have to find one that works.

 

Anyway the attraction is no requirement for using any kind of "cavity" filters which would be necessary on a more traditional in-band system. This means almost anybody could setup a repeater with far less technical expertise required and cost for a decent set of BPBR filters. So until the FCC changes the rules we won't have DMR on GMRS. I do expect that to happen sooner or later, likely much later.   

 

Yes, to a point.  BUT you loose the TDMA aspect of it. Meaning that you can only have a single talk path when operating like this and this mode will require everything to be brand specific.  Motorola will work with Motorola, Kenwood with Kenwood. 

Now mind you, I am a commercial radio tech.  But I don't see how not needing a duplexer is that big of a deal on a fixed repeater.  Due to the fact we are limited to 50 watts of power, the small mobile duplexers that are typically rated for 40 watts would do a fine job and they are inexpensive on the used market.  Yes, there is the tuning aspect, but that's not a big deal.

 

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