John's Musings

Yeah, Me Neither

A Newbie's DMR Primer

Bear in mind that I am a DMR newbie of sorts and this is a blog from the new dude discussing his opinions on DMR goodies and gotchas. I may get a technical detail or two wrong but I bet if I have this impression many other newbies would too.

There are two ways to connect to DMR.

  1. Digital Repeater
  2. Hotspot

Let me briefly discuss my understanding of connecting via a repeater. First of all your radio must be in range of the repeater. Once in range the repeater will have certain talkgroups that can be programmed into your radio. Here is an example from the repeater list. So if you are in the range of this repeater on Hoosier DMR these are the talkgroups that you can talk on when connected to this repeater.

Here's the closest repeater to me below. By the way I cannot reach this repeater from my home but can connect to it from in and around my office. This connects to the PRN DMR network.

So just for comparison if I want to talk to someone on the repeater in Muncie Indiana I'd have to do it on TAC 310. So simply you are a bit limited in talkgroup channels if you key in through a repeater.

The 2nd way to connect to a DMR network is via a hotspot. You use the internet to get into the DMR network. The most common way to do it is via the Brandmeister network. The Brandmeister network has some crossover with the DMarc network and such local networks as PRN which is the one closest to me. But Brandmeister has the MOST talkgroups. They are segregated dozens of different ways. If you want to get on DMR, and your goal was to talk to someone in Wyoming about the weather your best bet is Talk Group 3156, Wyoming Statewide. Here's the US BrandMeister talkgroups. Don't forget they have groups in other countries, and world wide groups etc. There is seemingly no limit to the groups you can listen in on or talk on.

The biggest problem with hotspot is that it is only as good as your internet connection and won't work at all if the internet breaks, gets hacked, EMP burst, etc.

That being said I think that most of us newbies are going to go the hotspot and Brandmeister route. So now you need a hotspot. I'm going to list some pros and cons of some of the more popular ones.

SharkRF Openspot

This might be the most popular hotspot out there (for the time being). And for good reason. It just works.

I bought one of these and initially didn't like it and I'll explain more about that here in a bit. I've grown to love it now though.

OpenSpot Pros:

  1. Attractive and well constructed
  2. Easy to connect
  3. Boots and connects fast
  4. Built in operating system already installed
  5. Easy to find on the network (sometimes)
  6. Can calibrate it for best modulation between your radio
  7. SharkRF has a opensource server program for Linux you can run to create private channels. (Very cool) I set one up here.
  8. Can cross platform between DMR and Fusion. You don't need two separate radios.

OpenSpot Cons:

  1. Expensive
  2. No Wifi. Ethernet Only.
  3. Web interface only. Cannot add OLED or Nextion screen.
  4. If set to DHCP it changes its IP address frequently
  5. Supposed to be able to find it in a browser at Openspot.local/ (doesn't always work on my network)
  6. Mine has reset itself a couple of times. Poof. Reset. (I do run the beta firmware though)

So you'll notice my first con is that it is expensive. It runs about $230 on a good day. That's steep but $230 plus a $90 radio will allow you to talk to anyone in the world. Back in the day $320 would barely pay for your coax, and antenna. Forget about the transmitter, tower, etc. $300 is a bargain to open the whole world up to you.

One of my pro statements was that it has a built in operating system. All of the other hotspots (almost) are boards that connect to a computer of some sort (i.e. Raspberry Pi, Orange Pi Zero, etc). I'm going to say this in bold for emphasis. While some the other hotspots are considerably less expensive essentially the operating system on the hardware board (i.e. Raspberry Pi) must be installed and configured by the end user. The OS used is Linux. Also if you opt to use a Raspberry Pi Zero W you better know how to solder because the header pins don't come installed.

So yeah, you can save some money but you have to know Linux well enough to install the OS, ssh or VNC into the OS, configure the wifi, etc. Then you have to possibly hand configure system files to get your hotspot to actually connect to the network.

Me. I love Linux. Been using it since the late 90's and man do I love to solder. So let's tackle the Pros and Cons of another board, shall we?


The DVMega is a HAT device which sits atop a Raspberry Pi or other small board computer. It comes in a UHF only or VHF/UHF board. Cost is about $129 for the UHF only and $169 dollars for the VHF/UHF board. Now consider this. Get the dual board, add a $35 Raspberry Pi, and a $10 SD Card and you're rapidly approaching the cost of the SharkRF OpenSpot. And there is no attractive case either. Just the boards.

Add a Nextion screen and it costs more than an OpenSpot however having a Nextion screen displaying all the necessary information that you as a Ham operator want to see is worth the extra expense.

DVMega Pros:

  1. Cheaper than OpenSpot
  2. Can utilize wifi from the Raspberry Pi 3 or Pi Zero W board.
  3. Can easily be used as a portable device in the car or camper. Use your cellular data for hotspot.
  4. Uses Linux! Yes that is a Pro for guys like me. Can tweak under the hood.
  5. Can easily connect an exterior OLED or Nextion LCD display screen.
  6. Raspberry Pi uses SD card. You can make up cards with various OS's and MMDVM instances and pick your favorite.

DVMega Cons:

  1. Uses Linux (yeah I know that bullet was a Pro as well) If you know nothing about Linux it is a Con.
  2. To upgrade the firmware requires soldering and mad Linux skills with one method.
  3. To upgrade the firmware with another method requires additional hardware and the removal and replacement of the IC chip on the DVMega.
  4. No case. Must make or 3D print one.

The DVMega is a sweet little board. Firmware programming is weird and the easiest way to program it I've found is just to program the chip in an Arduino R3 Uno. There are several nice cases that can be 3D printed for it. My favorite OS to use with it is Pi-Star. And just above I talked about the ability to add an external screen to the device. Having a Raspberry Pi underneath the DVMega allows for this. With a FTDI controller and a properly programmed Nextion screen attached you get access to all kinds of cool information. This feature is the OpenSpot killer in my opinion.

Let's move on to the Zumspot. Right at this moment there is no real link for Zumspot. Zumspot sits ideally on top of a Raspberry Pi Zero W.

Time for the Pros and Cons:


  1. Small. Small. Small. Can be used on Raspberry Pi Zero W (or Pi3)
  2. Portable. Perfect for the vehicle or camper
  3. Does P25.
  4. Like the DVMega you install Linux on the Pi.
  5. Easy to add OLED or Nextion.
  6. Comparatively inexpensive compared to the others ($99).


  1. If you buy just the Zumspot board you'll have to solder header pins on the Pi Zero.
  2. Zumspot is UHF only.
  3. Zumspot seems to ship with original firmware. Mine came with 1.01 and is currently up to 1.13.
  4. Currently there is no "Official" Zumspot website. Got firmware off a message board.

If I had this all to do over again I'd just buy 2 Zumspots. I'd slap one on a Pi Zero W and put it in the truck armrest console (I'm doing this now) and the other one I'd build up in a big fancy enclosure with a Nextion screen on it. (I'm doing this now with a DVMega). But think of the money I'd have saved with 2 Pi Zero W's, two Zumspots, and 1 Nextion screen. The Zumspot currently does all the digital modes to include P25 whereas most of the others don't do P25. If you aren't scared of Linux and even better not scared of running Linux completely headless.........get a Zumspot. They are awesome.

And lastly you have to figure that if something works well the Chinese will copy it and sell it cheaper. Such is the case of the JumboSpot or as some call it, the ChinaSpot.

$45 gets you a Jumbospot on eBay. I have one on order but don't have it yet. I've heard the gamut on the internet from "These work great" to "they are complete crap". I'll add to this blog and let you know as soon as mine comes in. There are multiple sources on eBay. I found one that had a lot of sales of the Jumbospot with good Feedback. One assumes there are multiple sources copying and selling these. Probably some are better than others.

JumboSpot Pros:

  1. Cheap. If you get a good one and it works you end up dropping about $65 total for your entire setup. That's awesome.
  2. Very easy to add an OLED display.
  3. Alum high quality enclosures available for just a few dollars. Fits the added OLED display perfectly.

JumboSpot Cons:

  1. Expect that once you drop your $45 for one that that's it. Don't expect a warranty. Pay extra for all the Paypal and eBay protections if $45 is painful to lose for you.
  2. From China. You spend your money, you take your chances.
  3. Many users are removing the ceramic antenna (labeled AE1 in the drawing above) and reporting lower Bit Error Rates having done so.
  4. Some horror stories with firmware updates.

Received my JumboSpot and added an OLED and fancy case. What can I say? It works. It works fine. Nobody says "Your other hotspot SOUNDS BETTER" or anything like that. For the amount of money I paid and what I received I'm extremely happy.

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