Understanding DMR repeaters and duty cycle

[MLee3008]

I'm new to the amateur radio world and trying to understand the digital options. In looking at DMR I ran across some info that seems to be conflicting. I thought one of the pros of DMR was to be able to find a talk group and listen at length if the discussion was interesting. There was some direction given from a club that said don't use our repeaters to go to these never ending talk groups. It was burning up their repeaters because the transmitters were running full power the whole duration. I would not want to be the cause of failure for someone else's equipment so I'm confused. Is the proper etiquette to contact the owner and ask permission to use his repeater? It sounds like a hot spot is a better option if I choose to go the DMR route, or it it a problem with D-Star and Fusion repeaters as well?

Mark

 

[Hit_Factor]

I don't understand comments like that. The repeater is likely to be largely unused otherwise.

 

[NoiseLimited]

It's one of those conveniently ignored fallacies of internet-connected repeaters. It's the same for D-star and Fusion. It sounds really good on paper - access to all these repeaters, reflectors and talk groups. In practice, tying up your local repeater to listen to them for an hour or two is not really practical. I don't know about burning up the machine as a lot repeater hardware is rated for 100% duty cycle - just maybe not for a hours at a time. Using the repeater to make a specific call is fine or to briefly have a qso in a group. But I'm like you, I like to listen mostly. And hotspots are the way to go if that's what you want to do. I just set mine up the other day for DMR. I still have and occasionally use my D-star dongle from years ago.

Good luck

 

[nd5y]

Is the proper etiquette to contact the owner and ask permission to use his repeater?

Always do that unless you are just passing through and/or don't intend to be a regular user.

It sounds like a hot spot is a better option if I choose to go the DMR route, or it it a problem with D-Star and Fusion repeaters as well?

The best thing about a hotspot is you have control over what talkgroups/rooms/reflectors you want to talk on or listen to. A repeater may be limited to only certain ones.

Repeaters need to be built with a transmitter that can handle continuous operation and not overheat. Some don't have enough heat sink capability to transmit at full power 24/7. Others, like the kind used in trunked systems, can transmit for years and never fail.

DMR repeaters transmit continuously during both time slots even if only one is in use.

I have read where some people have had new Yaesu System Fusion repeaters burn up.

 

[AI7PM]

Not all DMR repeaters, even from a single manufacturer, are 100% duty cycle rated. Ham clubs tend to buy the cheapest stuff, then gripe about repair and replacement costs later. Some of the lower end units are no more than two mobile RF decks mounted in a rackable box. Those are not designed to run for hours at a time. So yes, having those linked to a busy talk group for hours ata time is reducing the service life of the repeater. Ya get what you pay for.

 

[Project25_MASTR]

To further, many commonplace DMR repeaters (especially in the amateur community) are built off of mobile radio based platforms (the manufacturers did this for some reason). Notably, the Motorola XPR8300 is notorious for burning itself up (the fan needs to be either on full time or the thermsistor moved to the heatsink of TX radio, and not be located on the controller board). The XPR8400 fixed some of these issues but it is still quite possible to burn them up at their rated power ouptut (45W).

It's not like repeaters such as the Motorola MTR3000 and SLR series DMR repeaters which are built to be utilized as trunking repeaters (active control channels for 24+ hrs at a time). These repeaters are much more expensive, even in the used market, compared to the XPR8xxx repeaters and as a result...not very many amateurs want to fully understand the limitations of duty cycle just to put a repeater on the air.

 

[bharvey2]

In my area, there are quite a few DMR repeaters. While it isn't a problem to show up on one for brief transmissions and such, there are some owners who ask that they be reserved for specific talk groups. This is a reasonable request (as it is their repeater) Several years ago I opted to buy and set up my own hotspot allowing me to work any talkgroup I care to for however long I want. In fact when at home, I rarely talk on the local DMR repeaters unless I'm responding to a call I hear on one. I just use my hotspot. I think this is the best way to go for anyone intent on spending a good deal of time on DMR and avoiding becoming an unwanted guest on anyone else's repeater.

 

[vagrant]

When duty cycle is an issue, it would be prudent to turn down the TX power of the repeater and use a proper external amplifier that can handle the duty cycle and stay friendly with the duplexer. This would be performed by the repeater owner/club directly. Let the amp do the work and enjoy the repeater.

 

[popnokick]

Tx power amps for DMR are neither common nor inexpensive for repeaters in Amateur Radio service. And no... you cannot use a common FM power amp.

 

[bharvey2]

You're quite right Vagrant but I'm sure that's our of the OP's control. As was stated earlier, some ham people (and clubs) aren't exactly big spenders. Heck, I've seen posts on here about making repeaters out of two handhelds!?!

 

[OhSixTJ]

I think this is the best way to go for anyone intent on spending a good deal of time on DMR and avoiding becoming an unwanted guest on anyone else's repeater.

We’ve come full-circle and brought amateur radio into 2019 with a “don’t wanna use someone else’s repeated for fear they might get upset” mentality. “Use your own little hotspot and stay to yourself is the best option!”

Beginning of the end folks...


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[nd5y]

Just because it's a DMR repeater doesn't mean it's an open repeater that anybody can use.

 

[buddrousa]

I tend to disagree repeaters on PUBLIC HAM FREQUENCIES are open to the public. If you do not want the public to use them then do not put in a repeater. Now on the other hand IF YOU ARE GOING TO USE A REPEATER THEN HELP SUPPORT IT.

 

[OhSixTJ]

Just because it's a DMR repeater doesn't mean it's an open repeater that anybody can use.

Do you remember when owners who wanted to keep their repeaters private kept their repeaters private? Pepperidge farm remembers.

If it’s an open repeater then it’s an open repeater ¯\_(ツ)_/¯


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[krokus]

We’ve come full-circle and brought amateur radio into 2019 with a “don’t wanna use someone else’s repeated for fear they might get upset” mentality. “Use your own little hotspot and stay to yourself is the best option!”

Beginning of the end folks...


Sent from my iPhone using Tapatalk Pro

The hotspot option was not to keep to oneself, but remove the restrictions being applied by the repeater owner.

The portion I was curious about, is if the person was wanting to operate mobile/portable. If so, then a hotspot is not likely to work, unless you want to use a lot of cellular data.

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[OhSixTJ]

The hotspot option was not to keep to oneself, but remove the restrictions being applied by the repeater owner.

The portion I was curious about, is if the person was wanting to operate mobile/portable. If so, then a hotspot is not likely to work, unless you want to use a lot of cellular data.

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I’ve done that a few times. Haven’t run it 24/7 all month to see how much data it uses though. I do have an unmetered hotspot for hole internet that I run my jumbospot off of. Maybe there’s a way to check data consumption for that device through my routers software.


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[bharvey2]

I don't really have a problem with a repeater owner specifying his or her repeater as private or which talkgroups aren't welcomed. Keep in mind that with a DMR repeater open to all talkgroups, a timeslot could be tied up almost continuously with a wide area one like Nationwide or one of the Tac talkgroups. I frequent a system here in California that the owner/group put together to service California hams. Nothing wrong with that. Similar systems exist in Oregon and Washington as well as several other states. If I were to tie up time slot with an "Icelandic Cooking talkgroup" or some other obscure one for my own enjoyment, it could conceivably hog up quite a few resources depending upon how the repeaters were programmed. This hardly adheres to the "serving California" goal I mentioned before.

Bear in mind, I was never asked specifically not to utilize particular talkgroups on any system. In fact, I've never discussed the topic with any repeater owner or trustee at all. (Nor have I ever been asked to not use a repeater for that matter.) It really comes down to this: When I'm on a repeater, I have to "play well with others". With my own DMR hotspot or Allstar node, I can connect to whatever talkgroup or node I desire for however long I want.

 

[Hit_Factor]

I don't have numbers, but I loosely tracked data used for a month and hotspot data use was not much, compared to the rest of my data consumption.

 

[Project25_MASTR]

Tx power amps for DMR are neither common nor inexpensive for repeaters in Amateur Radio service. And no... you cannot use a common FM power amp.

Actually for a repeater, you can use a common FM power amp. It was commonplace to run XPR8380's at 10W of output into 150W Cresend amps built to service Kenwood LTR repeaters...I actually had an 8380 that ran like that as part of a Capacity Plus system for a decade before it was finally replaced by a MTR3000 (there were originally two at this site but the PA of one burnt up...at 10W).

For a DMR subscriber, you cannot use a regular FM amp. Either way, a 10 W in 100 W out FM amp rated for 100% duty is still in the $1500 range...2W in 100W out amps are about $2200 (another two hundred dollars and you can purchase an IPPA from RF Technology and vary your output independently of the 2W-5W input).

 

[MLee3008]

Interesting conversation. Thanks to all for taking the time to help educate me. Like I said in the original post I'm just trying to understand all the options available to see which one interests me the most. I'll probably go the hot spot route which if I understand correctly would allow me to try DMR, D-Star, and fusion to a certain extent.

I'm still confused a little on the public vs private use of repeaters. As buddrousa stated if it is on a ham band all should be able to be use it, and I agree 100% if I want to use one extensively it's only fair that I help pay for the maintenance of it. I also agree with NoiseLimited - most of the articles I've read say something to the effect of "Hey attach to a repeater and listen round the world for hours, whatever interests you." The only negative is about playing nice with others and don't commandeer and redirect for your own use at the expense of others.

Digital vs. analog voice is definitely something I want to research more. I just got a Yaesu FT-70DR and listening to some of the conversations shows a big difference between the two. It's like my younger days when I'd enjoy listening to an AM station from far away at night and then switching over to the local FM station. In my mind they both have their place.