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Digital Voice for Amateur Use - Discuss use of digital voice technologies on the amateur radio bands. This is to include technologies such as VoIP, P25, DMR/TRBO, NXDN, D-STAR, etc.

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Old 04-05-2018, 6:37 PM
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Default Amplifier for hotspots?

Planning on getting a hotspot or a more DIY approach. But looking at the specs of them, the 10 mW Tx power seems to be a deal breaker. Looking to get enough power to go around a 500 metres or a kilometre at.max. any way to do that? I guess conventional amplifiers won't work due to tdma :s

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Old 04-05-2018, 6:39 PM
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Originally Posted by S21IL View Post
Planning on getting a hotspot or a more DIY approach. But looking at the specs of them, the 10 mW Tx power seems to be a deal breaker. Looking to get enough power to go around a 500 metres or a kilometre at.max. any way to do that? I guess conventional amplifiers won't work due to tdma :s

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Not sure but you might run into coordination issues running higher power. Have you maximized antenna and coax efficiency?


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Old 04-05-2018, 6:49 PM
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Not sure but you might run into coordination issues running higher power. Have you maximized antenna and coax efficiency?


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Didn't get one yet. Looking to explore my options before purchasing one. As sad as it gets, don't have a single amateur DMR repeater in the country leaving me no choice but to get a hotspot. But the TX power seems to be the limiting factor. Seems fairly pointless spending $500++ on a radio+hotspot if that doesn't get me past my shack

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Old 04-05-2018, 6:59 PM
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Quote:
Originally Posted by S21IL View Post
Planning on getting a hotspot or a more DIY approach. But looking at the specs of them, the 10 mW Tx power seems to be a deal breaker. Looking to get enough power to go around a 500 metres or a kilometre at.max. any way to do that? I guess conventional amplifiers won't work due to tdma :s

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I saw this YouTube video online. The amplifier is pretty stout so I would say you can turn the transmit power down to the needed range.

I hope this video helps!

https://youtu.be/nyaK6tN8i7w
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Old 04-05-2018, 7:02 PM
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Thanks for the link! Will check it out.

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Old 04-05-2018, 7:11 PM
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If you won’t interfere then might work but I am not an expert on your nations coordination rules.

I’ve often thought about treating hotspots like microrepeaters. This would have a cellular phone structure covering an area. Reduces repeater costs and allows better coverage where people would use it.




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Old 04-05-2018, 9:08 PM
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These amplifiers are designed for much greater power than what the hotspots put out and may not key up reliably. I also see the build quality of the Chinese amps is very questionable.
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Quote:
Originally Posted by N2AL View Post
I saw this YouTube video online. The amplifier is pretty stout so I would say you can turn the transmit power down to the needed range.

I hope this video helps!

https://youtu.be/nyaK6tN8i7w
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Old 04-08-2018, 9:15 AM
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Anyway to interface hotspots to a repeater?

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Old 04-08-2018, 9:33 AM
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Originally Posted by S21IL View Post
Anyway to interface hotspots to a repeater?

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What digital mode or modes are you attempting to interface to a repeater? That would determine exactly what option works best but likely the MMDVM would be your best bet (doesn't reliably do NXDN from what I understand but will run everything else).
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Old 04-08-2018, 9:55 AM
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Originally Posted by S21IL View Post
Anyway to interface hotspots to a repeater?

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Depending on whether or not the hotspot could do offsets it could simply be shotgunned but if not you'd have to setup the repeater for a simplex link.

To answer the OP's original question 500 meters is only 79 dB of path loss in the 70 cm band. 1 km would be 85 dB of loss. So RX signal would be between -70 dBm and -75 dBm if we are talking about being out in the open (which still leaves 35+ dB of link budget on even the worse subscribers).
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Old 04-08-2018, 10:56 AM
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Originally Posted by N1GJB View Post
What digital mode or modes are you attempting to interface to a repeater? That would determine exactly what option works best but likely the MMDVM would be your best bet (doesn't reliably do NXDN from what I understand but will run everything else).
I just need DMR

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Old 04-08-2018, 11:43 AM
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https://m.ebay.com/itm/50W-UHF-400-4...kAAOSwXf9ZpT0b

Found this on eBay. Doesn't seem to have any information on the gain of this. And also says it works with 1.5W of power on the input. How feasible would this be with 10-50mW on input?

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Old 04-08-2018, 11:56 AM
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This is a really bad idea. The hotspot was intended to be just that, a hotspot. Not a wide area device. If you can even kludge an amplifier on to it, hotspots don't have all that great of a receiver. So you may be able to make it talk, but it may not hear you very well.

The other thing is, if you do find an amp, like someone else said, it will probably come from China and throw spurs and other IMD products all over the band which will piss off your frequency neighbors.

After all this trouble, in the long run you are better off to just put up a small repeater. You could use a MMDVM modem and a used commercial repeater. You could buy a used Motorola XPR series repeater and just "plug it in". The repeater doesn't need to be a powerhouse. 25 watts or less is all you will need.
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Old 04-08-2018, 12:02 PM
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Originally Posted by R8000 View Post
This is a really bad idea. The hotspot was intended to be just that, a hotspot. Not a wide area device. If you can even kludge an amplifier on to it, hotspots don't have all that great of a receiver. So you may be able to make it talk, but it may not hear you very well.

The other thing is, if you do find an amp, like someone else said, it will probably come from China and throw spurs and other IMD products all over the band which will piss off your frequency neighbors.

After all this trouble, in the long run you are better off to just put up a small repeater. You could use a MMDVM modem and a used commercial repeater. You could buy a used Motorola XPR series repeater and just "plug it in". The repeater doesn't need to be a powerhouse. 25 watts or less is all you will need.
This is the option I'll go for hopefully. As we don't have any DMR repeaters here in the country. Have it connected to the BrandMeister network maybe..

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Old 04-08-2018, 12:04 PM
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Going a bit off topic, how'd the hotspot run on mobile data? I mean would the latency introduce any issues with TDMA?

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Old 04-08-2018, 3:12 PM
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Going a bit off topic, how'd the hotspot run on mobile data? I mean would the latency introduce any issues with TDMA?

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I have never had issues. I used to run the internet connection from my cell phone but now I use my wifi connected to a RaspberryPi connected to the OpenSPOT.

According to my RaspberryPi it uses about 4GB per month. That is with constant use by the way. I cannot account for your situation but I doubt it would be too excessive.

Anyone else have some insight?
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Old 04-13-2018, 9:52 PM
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If you want wider coverage, build yourself a DMR repeater of some sort using a pair of mobile radios and a digital modem like the MM-DVM, if you can afford to have one shipped to your country (if they will do it). Here in the States, you can get cheap Motorola radios with a repeater interface cable on eBay for a decent price, then find a way to wire in the MMDVM to them, and you're off to the races.
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Old 04-14-2018, 2:21 AM
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If you want wider coverage, build yourself a DMR repeater of some sort using a pair of mobile radios and a digital modem like the MM-DVM, if you can afford to have one shipped to your country (if they will do it). Here in the States, you can get cheap Motorola radios with a repeater interface cable on eBay for a decent price, then find a way to wire in the MMDVM to them, and you're off to the races.
That's the plan I've had. Can get the MMDVM, also the Motorola mobiles but stuck because I don't own the CPS, no one I know does and to top that off, we don't even have a dealer who could do it for me

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Old 04-14-2018, 6:37 AM
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I installed a small fiberglass stick on my hot spot due to the fact its in by my cable router in my parents house a couple hundred feet from me. It seems to work well although im sure the loss factor is pretty good, but i have an sma adapter to the N(M) on the antenna. Works for me but YMMV
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Old 04-14-2018, 5:21 PM
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That's the plan I've had. Can get the MMDVM, also the Motorola mobiles but stuck because I don't own the CPS, no one I know does and to top that off, we don't even have a dealer who could do it for me

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Get a couple of cheaper but reliable Connect System CS800s. The D model is dual band. The non D model is mono band (either VHF or UHZ). The nearest vendor might be in the UK but double check.


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