DMR distances

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Re: DMR distances

Postby mickydt » Sun Jan 20, 2019 2:57 pm

i am picking up a dmr frequency in the 450mhz band. me and Andrew on here got in to a tizz about it as i got it as a local car park frequency but yet Andrew said it was heysham port, well if that is the case then that is some miles from where i am it puts it around 7 miles.

also again years ago it was used by the old ambulance portables.
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Re: DMR distances

Postby Alfie » Sun Jan 20, 2019 5:35 pm

G4RMT wrote:I'm intrigued with this notion that DMR doesn't go as far. In the commercial sector the main selling point is that digital stays good out to the fringes, when it suddenly just dies, rather than becoming broken up. That to me is more usable range. Digital audio has always like this - it works wonderfully until it doesn't.

Hmm so digital dies completely where analogue will be scratchy and breaking up ? just that statement alone says you can here analogue at a further distance. also digital does break up and goes garbled when getting out of range and sounds horrible and unhearable.

have you tested range and monitored and analyzed an analogue and DMR signal from a standard 5 watt radio ? we have using the same spec radios and same 5 watts (motorola gp analogue radios vs motorola dmr dp radios) and at the same power analogue is superior when it comes to range. look at the signal stream tx itself. analogue is a full on full power constant stream where dmr is a choppy stream that goes up and down on the power scale. plus there is decoding involved not needed on analogue. these factors alone show side by side using same spec/power that analogue is better at a further distance. i think there is a lot of mis info about digital fooling people that the science itself does not support. for example my boss actually thought the same as he was hoodwinked. we used 1 watt analogue radios simplex on a rather large site. this was upgraded to a duplex dmr system at a higher wattage. he thought digital was so much better. that was until we went off the repeater channel and compared 1 watt dmr simplex to our older 1 watt analogue radios on site and the analogue were far far more superior. this was before the end of year accounts when my boss first saw the cost difference and nearly fainted. he reported our findings to management and needless to say the dmr repeater was gone 4 months later which would have been earlier but it was paid up for another 4 months. and the site is now using once again analogue radios although now at 5 watts with no coverage problems and no need for a repeater either analogue or digital and a hell of a lot cheaper.

to be honest i think most of the people saying digital is the same or better range are mostly radio suppliers trying to push the new digital tech and talking complete tosh. others are those that have been hoodwinked too. no offense meant. digital has a lot of benefits analogue does not but better range with the same spec equipment ?? i dont think so :mrcool:
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Re: DMR distances

Postby G4RMT » Sun Jan 20, 2019 7:15 pm

OK - if you are a radio ham, then you are skilled at hearing a noisy, broken up signal, recognising the problem and holding the radio over your head to get the last squidge of signal. People who use communications for their work or business want readable signals. Broken up ones are useless. They also want a radio that can be in the pocket, or laying on a seat - not propped up in the window.

For work, I used to be an Icom user, but I moved to Kenwood, and I have my older hire kit on FM - which is either through my repeater, mobile repeaters or back to back, and around a dozen are 300 series digital. All have analogue channels and the 300s have digital too. In practice, there is no practical difference is range - up to the point where the FM radios get scratchy and broken.

Your understanding on the choppy form of digital streams is simply wrong. If signal strength is poor, digital will suffer - quite badly, but I support the manufacturers claims about intelligibility being better (once you get used to the slightly robotic voices, of course). As soon as FM is no longer fully quieting, then problems start with the background noise increasing, CTCSS tones getting lost and choppy audio. The intermittent nature of the data stream makes no practical difference. My few DMR radios have exactly the same performance as the narrow band continuous stream NXDN units. You have X amount of data - you can break it into packets that follow each other contiguously, or there can be a gap for two channels in the one space. If the quantity of data gets to the other end intact it works.

I totally agree with the scenario where your area means you will have fringe coverage in too many places. Analogue FM is better. However, this also means the system is poorly designed - with too much path loss for reliability. Sure - your working FM system appears to be better, and it is, because not performs. Digital in fringe areas is not good. Same on your phone. The analogue cellular network worked better for the same reasons, but by adding more nodes to the system, it gets better and digital works.

Digital comms is more modern, offers more facilities can handle more users. It does have less range, but up to the point where it drops below threshold, it hold up better.

We're talking about signal strength, nothing more. It's bad practice to work a system at its fringes. If you want more range, then improve the antenna system on the repeater, or add another repeater. I've got analogue kits and many different types of digital - many that don't work with each other, but range has never been an issue. If I get a job where radio to radio will be a problem, I supply a repeater. If it's a long thin site, then I design in a suitable antenna system to let it work. Frankly, if people want to have radios in inside pockets under many layers, then we're talking about a few hundred yards on a 5W radio (or a 1W one to be fair) Analogue or digital is fine for me. If you want to squeeze the last bit out of your range - then FM makes sense, but at this distance, putting the radio in your pocket means you hear nothing. Let's be honest - a £25 Baofeng works very similarly to a £500 Motorola. Distance is NOT what you are paying for.
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Re: DMR distances

Postby JohnUK » Sun Jan 20, 2019 8:33 pm

CW-2E0UCW wrote:
JohnUK wrote:
mickydt wrote:picking one station up with what sounded like Liverpool accent and this morning i confirmed that they are based somewhere around the Liverpool area just goes to show.

Was it 152.1125 by any chance?

The nearest hit on that frequency is for DCS 2 Way Radio Limited (L5 3QC) -

Yes that's the one I listen to I think. I mentioned 152.1125 as I am roughly 100 miles away from Liverpool and Everton however on this frequency I hear the taxis there in DMR and quite clearly so I assumed that was what mickydt might be hearing. When the WTR was in it's old format I looked it up and I think it was in Frodsham? Or it could have been Everton? My PC doesn't like the new WTR so I don't use it unless I have a few hours free as every click takes minutes to load.
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Re: DMR distances

Postby Chris P » Sun Jan 20, 2019 9:07 pm

Probably was Frodsham or more accurately Overton hill . As a child in the 50`s I remember the radio masts on the top of the hill with a view across the rivers weaver and Mersey as far as Liverpool and Birkenhead, so a good site for a repeater.
There are also good views from the hill towards Delaware forest to the SE even as far as Stoke on Trent and apart from the curvature of the earth no higher ground between (as seen on Solwise elevation tool)
Regards Chris aka G8FFF nipper or tazmin88
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