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who uses DMR within raynet

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M3AWY View Drop Down
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    Posted: 02/July/2016 at 20:48
afternoon all members 
i would like to know who uses DMR within raynet as im trying to guild my group to go that direction instead of fusion ,


i have been in the pmr industry for the past 17 years and im the groups equipment officer , with my experience of dmr , and also being a Motorola engineer , im fully aware of what the trbo range can do and have shown the group.


so i would like to know who uses dmr .



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G1HUL View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote G1HUL Quote  Post ReplyReply Direct Link To This Post Posted: 03/July/2016 at 08:56
Not using DMR in RAYNET yet, but looking in that direction (so this is probably a half-way answer!).

All the digital modes that have been offered within the hobby so far have been single-sourced and very expensive (D-STAR, Fusion), limiting take-up as people don't see the justification for replacing their kit for little benefit. Yaesu are the closest to industry standards having adopted C4FM (dPMR), it's their own implementation so you can't use any dPMR radio. There have been rumours over the last couple of years of Kenwood planning a D-STAR radio, but it all seems to be vapourware.

DMR seems to have the biggest commercial market penetration by a very wide margin (even Kenwood now have commercial DMR sets as well as NXDN/dPMR to ensure they aren't missing out on the action!). The American P25 network has also switched from dPMR to DMR in Phase II.

Considering all the DMR equipment available is currently commercial, there are a huge number of amateur DMR repeaters on air, more than any other digital mode so far. There have also been a number of D-STAR repeaters converting to DMR. I believe this is fuelled by the easy availability of cheap Chinese sets (TYT MD-380 for example - I have a couple sitting next to me as I type this!) attracting people into the mode.

The Amateur's "holy grail" of a dual-band set will never happen from the commercial world, but the DV4MOBILE was recently announced as an all-digital-mode DSP-based mobile set. maybe a couple of years off, but we're getting there!

Anyway, enough waffling suggesting why DMR is the future Big smile


ID, short messaging, linked repeaters, individual calls, etc. etc., digital modes have a lot to offer RAYNET.

Digital is not everyone's cup of tea (both from those who don't want digital for a variety of reasons, and those who believe amateur's should only use amateur-market equipment) so will always be a "niche" part of our operations with FM always being the common denominator, but the low cost of DMR will encourage people to upgrade and if enough people in a Group get the kit, it could become an important part of the services we provide to our users.

The repeaters are not cheap so it will only be the better-off groups who are able to buy the kit to support digital operations, but there are some designs around for amateur-built solutions so even this barrier will drop over time.

My worry about digital in the RAYNET environment is the lack of knowing the health of the network - i.e. what the signal quality is like. We are experts at getting messages out of a fading/weak/fluttery signal at levels way below that of digital decoding, but also recognising that there is a growing problem with signals before they impact the operation.

None of that with digital, it's the cliff-edge before you have any idea that there is an issue, at which point you switch to FM to diagnose what's going on with the signal level LOLLOL


An interesting aside on the technical merits of TDMA(DMR) -v- FDMA(dPMR). A friend of mine is involved in high-end motorsport comms and when digital first appeared on the market they evaluated both systems. The result was firmly in favour of FDMA.

In short, they found that the slot sync time required for TDMA was a significant problem from a racing car due to high-speed mobile flutter, whereas FDMA just requires the bit sync time (obviously common to both modes).

Perhaps this isn't a consideration for RAYNET (although 6.25KHz FDMA also has better range), but illustrates why the system with the biggest market penetration isn't necessarily the best system technically for a given application (remember VHS-Betamax...).



Jim

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M3AWY View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M3AWY Quote  Post ReplyReply Direct Link To This Post Posted: 03/July/2016 at 16:04
Hi Jim 
thank you for your input,

yes dont get me wrong dmr is not perfect by any means but for the operational requirements of raynet it fits the bill perfectly, 

when you have the full scope of kit available the options are endless of we could do with the dmr trbo range.


  
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G1HUL View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote G1HUL Quote  Post ReplyReply Direct Link To This Post Posted: 03/July/2016 at 20:21
As was once said to me by Greg (G0DUB)...

Standards are great, there are so many to choose from Stern Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M0NLP Quote  Post ReplyReply Direct Link To This Post Posted: 04/July/2016 at 11:04
Several of the groups in Kent are playing with DMR too.  In West Kent we don't have a repeater that covers much of our patch yet, but the rest of the county is served quite well.

Although Phillips 2000 was better than Betamax, VHS still won that battle. With a backround too in PMR any other digital mode is unlikely to exceed the hold on the market, and hence the availability of knowledge as well as better prices on the kit.

As an engineer it is difficult sometimes to chose between what is the "best" and what is the "sensible option"

The sensible option if ever we take digital to deployments in place of anything else it will be DPMR.  At this stage we are still playing and learning.  There are more DPMR sets in my group than the total of other digital modes combined.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote G1HUL Quote  Post ReplyReply Direct Link To This Post Posted: 04/July/2016 at 11:43
Originally posted by M0NLP M0NLP wrote:

There are more DPMR sets in my group than the total of other digital modes combined.


Interesting that people have gone the dPMR route, which is the least supported amateur mode in terms of repeaters.

Which sets are you using, as I haven't seen much in the way of cheaper dPMR kit?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike G7HEN Quote  Post ReplyReply Direct Link To This Post Posted: 04/July/2016 at 16:14
Originally posted by M3AWY M3AWY wrote:

Hi Jim 
thank you for your input,

yes dont get me wrong dmr is not perfect by any means but for the operational requirements of raynet it fits the bill perfectly, 

when you have the full scope of kit available the options are endless of we could do with the dmr trbo range.


  


The problems we can see, are the linking of the repeaters and the lack of 2m channels for in-band repeaters.

Mike G7HEN

Keighley RAYNET Deputy Controller
http://www.raynet.keighleyradio.co.uk

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Post Options Post Options   Thanks (0) Thanks(0)   Quote M0NLP Quote  Post ReplyReply Direct Link To This Post Posted: 05/July/2016 at 09:15
I would like to correct the mistype in my final line - I should have typed DMR.  We have more DMR sets in our group than all the other technoligies together

I was writing a codeplug for a DPMR set at the time on the other computer!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote M3AWY Quote  Post ReplyReply Direct Link To This Post Posted: 05/July/2016 at 20:04
Aha I think I have proved a point I think.

DMR is the way forward for Raynet as time goes on more and more user services are moving over to dmr.

And a simple repeater can be built very cheaply
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike G7HEN Quote  Post ReplyReply Direct Link To This Post Posted: 05/July/2016 at 20:35
Originally posted by M3AWY M3AWY wrote:

Aha I think I have proved a point I think.

DMR is the way forward for Raynet as time goes on more and more user services are moving over to dmr.

And a simple repeater can be built very cheaply

Yes but how do you link two or more repeaters together


Mike G7HEN

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http://www.raynet.keighleyradio.co.uk

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