Hanging out with hotspots

By Toshen, KEØFHS (Updated Jun 2018, CC BY-SA)


A hotspot (personal access point) is a combination of hardware and software that enables a ham with internet connectivity to link directly to digital voice repeaters, D-STAR reflectors, QuadNet Smart Groups, DMR talkgroups, YSF rooms, etc. Basically, these devices act as your personal digital voice repeater and gateway.

This illustration shows what it looks like for D-STAR:

Diagram of DV HTs connecting via personal access points to a reflector and a DV repeater

For someone like me who doesn't live within range of a digital voice (DV) repeater, a hotspot is an important key to accessing digital voice systems, a gift that opens doors to the whole wide world.

I've been playing around with hotspots since Oct 2016. During this time, I've tried a bunch of different hotspot devices and apps. Overall, it's an exciting area of amateur radio that is evolving and progressing rapidly with some excellent work being done by innovative hams. I'm really grateful for everything I'm learning!

Disclaimer:  These are my personal notes and opinions based on using hotspots and from what others are sharing. I've tried to be accurate, but if you come across anything needing correction, give me a holler.

1) Hotspot hardware

There are many different hotspot hardware devices being developed by innovative hams to work with the different flavors of digital voice:

Important hints!

⊙ ZUMspot

Designed by Jim Mclaughlin, KI6ZUM, with firmware by Andy, CA6JAU (GitHub: juribeparada / MMDVM_HS⩘ ), based on the MMDVM software by Jonathan Naylor, G4KLX (GitHub: g4klx / MMDVM⩘ ).

ZUMspot boardThe ZUMspot is a multimode digital voice modem that works with D-STAR, DMR, YSF, P25, and NXDN, as well as YSF and DMR cross modes. It's the same size as a Raspberry Pi Zero W and works really well mounted on it as a hat. It also can be mounted on the RPi 3 and various other RPis. Requires a digital-voice capable radio (includes a stubby antenna).

The ZUMspot is currently my default hotspot in my shack for D-STAR and DMR, the two digital modes I use. It pairs well with the Pi-Star software, discussed below, and its firmware can be updated easily via Pi-Star's command line: Performing firmware updates via Pi-Star⩘ .

The ZUMspot is availabe from Ham Radio Outlet: ZUMspot Pi Board⩘  or ZUMspot Kit⩘  (kit version includes a Raspberry Pi Zero W).

See also the note below: Zooming around with ZUMspot.

⊙ MMDVM_HS_Hat (the genuine one)

Created by Florian Wolters, DF2ET and Mathis Schmieder, DB9MAT (GitHub: mathisschmieder / MMDVM_HS_Hat⩘ ).

(I'm guessing that "HS" might stand for "hotspot.")

MMDVM_HS_Hat boardThe MMDVM_HS_Hat is a Multi-Mode Digital Voice Modem Hotspot Hat board made by hand of quality components that fits nicely on a Raspberry Pi Zero W, and works with D-STAR, DMR, YSF, P25, and NXDN, as well as YSF and DMR cross modes. Requires a digital-voice capable radio.

The MMDVM_HS_Hat is available in two versions, one with an onboard ceramic chip antenna, as shown above, and another with an SMA socket external antenna. Pictured is version 1.6 with the onboard ceramic antenna as well as the new 12.288 MHz onboard TCXO.

MMDVM_HS_Hat firwareIt works well with Pi-Star, discussed in the software section below, and its firmware can be updated easily via Pi-Star's command line. See the note: Performing firmware updates via Pi-Star⩘ . Set up was easy, especially because it can use Pi-Star's Auto AP feature for wireless network configuration.

Because of the extra compactness gained with a ceramic chip antenna, it has become my new mobile hotspot (an SMA socket external antenna seems to me to add a degree of fragility to a hotspot; frankly, I'm always a little concerned I'm going to inadvertently knock it off). The MMDVM_HS_Hat fits nicely on the rugged RAVPower 10050 mAh battery pack that I use as my portable power supply.

MMDVM_HS_Hat mobile hotspot
For more about this case, see the note below: 7) Dissecting a hotspot case.

To order, email the developers directly: mmdvm@df2et.de. It's quite reasonably priced, though you need to be patient as there tends to be a waiting list, and once they have made the board, shipping from Germany to the U.S. takes another several days. It's worth the wait!

If you're good at assembling electronics, you can Build your own MMDVM_HS_Hat⩘ , and there's a pre-configured Mouser cart for version 1.6⩘ .

Note: There's also a design for a Dual Hat board by Mathis, DB9MAT, Florian, DF2ET, and Andreas Meier, DO7EN, posted on GitHub:
phl0 / MMDVM_HS_Dual_Hat⩘ .

See also the note below: 6) Beware of unauthorized clones.


Created by Guus van Dooren, PE1PLM, Dooren Electronic Solutions.

DVMEGA-UHF mounted on Raspberry Pi boardThe single-mode (UHF) DVMEGA is pictured mounted on a Raspberry Pi 3, and there are other models as well, including dual-mode VHF/UHF, pictured below. With firmware 3.07 and later, the DVMEGA can support D-STAR, DMR, and YSF. Requires a digital voice-capable radio (includes a mount for a stubby antenna).

DVMEGA-DUALThe DVMEGA was my default D-STAR hotspot in my shop for the first year or so I used D-STAR, and I still think it's a solid choice. It's dependable, pairs well with Pi-Star, and once you've soldered the firmware update jumper wire in place, it's easy to update via Pi-Star's command line. For maximum flexibility, I chose the DVMEGA-DUAL (VHF and UHF); however, I've only used UHF frequencies, so the less-expensive DVMEGA-UHF would've been fine. That said, the DUAL is a more compact board.

One minor irritant: The standoff hole is designed for the BlueStack (see below). When the DVMEGA is mounted on an RPi 3, there's nothing below the hole to connect a standoff to, so the only thing holding the hat down is the GPIO connector. Consequently, since the antenna mount is in the corner diagonally across from the connector, if the connector isn't glued down in some way (for example, with hot glue), the standoff acts like a pivot: if you touch the antenna, the connector tends to lift off the GPIO pin header.

For firmware info, see the note: DVMEGA firmware update⩘ .

In the U.S., the DVMEGA is available from various shops.

More info: dvmega.auria.nl⩘  or @GuusvanDooren⩘ .

⊙ BlueStack-Micro+

Created by Ruud Kerstens, PE1MSZ.

BlueStack-Micro-plus boardThe DVMEGA RPi board also can be paired with a BlueStack-Micro+⩘  board instead of an RPi, which enables bluetooth connection to an Android phone running BlueDV for Android⩘  or a serial connection to a Windows computer running BlueDV for Windows⩘ . (There also are experimental versions available for iOS, RPi, and Linux.)

When powered by a portable battery pack, the BlueStack + DVMEGA combination provides a mobile solution that can be used with D-STAR, DMR, and YSF radios. For more about this mobile solution, see: Just can't wait to get on the road again⩘  in my D-STAR article.

BlueDV running on Android

The BlueStack board also can be used to facilitate a DVMEGA firmware update. For more info, see the note: DVMEGA firmware update⩘ .

I originally ordered my BlueStack-Micro+ board directly from Combitronics⩘  in The Nederlands, but in the U.S., it's now available from various shops.

More info: pe1msz.nl⩘ .

⊙ SharkRF openSPOT

Created by Ákos Marton, HG1MA, and Norbert Varga, HA2NON, SharkRF.

SharkRF openSPOT

This is a high-quality, standalone device, but it doesn't have built-in WiFi, so it does require a wired connection to a router. Works with a D-STAR, DMR, or YSF radio. Quite easy to set up and use. Includes a stubby antenna, power supply, and all the necessary cables.

Unique among all of these hotspots, they have excellent online documentation: openSPOT User Manual⩘ .

The openSPOT was my default DMR hotspot for the first year I used DMR. For more info, see: Choosing a hotspot⩘  and A couple openSPOT hints⩘ .

I also was able to use the openSPOT to create a mobile hotspot by connecting it to a nano router that was in turn connected wirelessly to my Android phone acting as a portable WiFi hotspot. See: On the road with the openSPOT⩘ .

Although I liked the openSPOT, once I started using the MMDVM-based hat boards with Pi-Star, I didn't use it anymore and ended up giving it away.

In the U.S., the openSPOT is now available from various shops.

More info: ⊙ SharkRF openSPOT⩘ .

⊙ Micro-Node Nano-Spot

Micro-Node Nano-SpotCreated by Mark Guidbord, K7IZA.

Note: I haven't yet tried this hotspot, but if you're looking for hotspot hardware, it looks like one that's worth checking out.

The Nano-Spot appears to be a nifty little plug-n-play device. It includes built-in WiFi, RF and WiFi antennas, and an OLED display, all in a durable extruded aluminum case. Runs Pi-Star. Requires a digital radio and supports D-STAR, DMR, YSF, and P25.

Could be a nice, ready-made solution.

More info: ⊙ Micro-Node Nano-Spot⩘ .

⊙ NW Digital Radio ThumbDV

NW Digital Radio ThumbDVCreated by Bryan Hoyer, K7UDR, Basil Gunn, N7NIX, John Hays, K7VE, and Dennis Rosenauer, AC7FT, NW Digital Radio.

Note: I haven't yet tried this hotspot, but if you're looking for hotspot hardware, it looks like one that's worth checking out.

The ThumbDV is a USB device with a built-in AMBE chip, so it can be plugged into a computer that has a microphone and speaker, and doesn't require a digital radio. Depending on the hotspot software used, can support D-STAR, DMR, and YSF. [ThumbDV PDF⩘ ]

More info: NW Digital Radio ThumbDV⩘ .

⊙ DV Access Point (DVAP)

Created by Robin Cutshaw, AA4RC, and Moe Wheatley, AE4JY, Internet Labs.

DV Access Point dongleThese good quality devices, one of the earliest hotspots available, can be connected to a PC running Windows or a Mac. Requires a D-STAR radio. When running their own software, the DVAPs only with DPLUS (REF) reflectors, intentionally block access to XRF, DCS, and XLX reflectors, and don't support DMR, YSF, or P25; consequently, I found this to be a restrictive solution and ended up giving my DVAP away.

More recently: I learned that the Pi-Star app supports the DVAP. I haven't tested it but hopefully all the D-STAR modes are supported, including XRF and DCS.

More info: DV Access Point (DVAP)⩘ .

⊙ DV4mini and DV4home

Created by Uli Altvater, AG0X/DH6SAB, and Torsten Schultze, DG1HT, Wireless Holdings.


Another one of the earliest personal hotspots that was available, the DV4mini is a USB stick that can plug into a PC running Windows or Linux, or a Raspberry Pi. Includes a mount for a stubby antenna, requires a D-STAR, DMR, or YSF radio.

The DV4home is a standalone digital voice device that has two AMBE chips as well as its own screen, microphone, and speaker.


While I know people who use and like the DV4 devices, I personally found both the DV4mini and the original DV4home V1 clunky to use when I tried them in late 2016, and ended up giving them away. The DV4home's rotary knob was particularly poorly implemented—I found it almost unusable—and I've heard similar feedback from someone using V2. Too bad, because I had high hopes for using the DV4home as my digital base station … and it was expensive!

More info: Wireless Holdings⩘ .

2) Hotspot apps

There's also all sorts of different hotspot apps available:

⊙ Pi-Star

Created by Andy Taylor, MW0MWZ.

Pi-Star works with many devices, can be used in hotspot or repeater mode, and supports DMR, D-STAR, YSF, P25, and NXDN. I've run Pi-Star on Mac, Windows, Android, and a Raspberry Pi. It works really well, is feature rich, and is enthusiastically developed and supported by Andy and team. It has a very good user support forum, the Pi-Star User Forum⩘ .

Pi-Star dashboard

Pi-Star is my favorite hotspot app for the two digital radio modes I use: D-STAR and DMR. At this time, I'm using Pi-Star with a ZUMspot mounted on a Raspberry Pi 3 in my shack, and with a MMDVM_HS_Hat (the genuine one) mounted on a RPi Zero W for mobile use. Initially, I used it with a DVMEGA mounted on a Raspberry Pi. They're all great combinations, though the ZUMspot and MMDVM_HS_Hat have the advantage of P25 and NXDN support.

My full article about configuring and running Pi-Star: Playing with Pi-Star⩘ .

More info: Pi-Star⩘ .

⊙ BlueDV

A hobby project by David, PA7LIM.

This app can be run on Android and Windows (experimental versions of BlueDV are also available for iOS, Linux, and RPi), and is a great solution for creating a mobile hotspot using the BlueStack-Micro+⩘  paired with a DVMEGA board.

DVMEGA & BlueStack in custom case

For more info about using BlueDV as a mobile hotspot, see: Just can't wait to get on the road again⩘  in my D-STAR article.

There's also an interesting new "pre-beta" ¹ feature available: DMR Simple Mode. All you need to do is add talkgroup 9, color code 1 to your radio for connecting to your hotspot, and then you can switch to other talkgroups in the app itself.

BlueDV running on a PC

[1] David labels all of his apps beta, pre-beta, or experimental. In my own experience, his beta builds are what most people would call release versions, and his pre-beta builds are what most people would call beta. His stuff is really good. Of course, there's room for improvement, but that's true of all the apps in the world! He's doing really innovative work to push the boundaries of digital voice, which I really appreciate.

More info: BlueDV⩘ .

⊙ SharkRF openSPOT

Created by Ákos Marton, HG1MA, and Norbert Varga, HA2NON.

Works with the SharkRF openSPOT device. Relatively easy to use. Supports DMR (Brandmeister, DMRplus), D-Star (DCS, REF/DPlus, XRF/DExtra, XLX), YSF (FCS, YSFReflector), as well as cross mode between DMR and YSF (use your DMR radio to talk on YSF networks and vice versa). The openSPOT was my default DMR hotspot for the first year I used DMR.

See also: Choosing a hotspot⩘  and A couple openSPOT hints⩘ .

More info: SharkRF openSPOT⩘ .

⊙ DStar Commander

Created by Bob Scott, W6KD.

Compatible with the RPi models B, B+, 2B, 3B and Zero/Zero W(ireless). Works well with the DVMEGA device, but also can be used with some other devices.

DStar Commander was my default D-STAR hotspot app in my shack for the first year I used D-STAR, and I really appreciate that it helped launch my journey into digital voice radio. However, it seems to be in maintenance mode, with no new updates in a long time. And it appears that Bob may not update it for the RPi 3B+, and is instead pointing people to Pi-Star and the KB5RAB image⩘ .

More info: DStar Commander⩘ .

⊙ DVAPTool

Created by Robin Cutshaw, AA4RC, and Moe Wheatley, AE4JY.

For running the DVAP Dongle. I tried DVAPTool and found it worked fine, but because of the DVAP's limitation of working only with DPLUS (REF) reflectors, I found it an insufficient solution and ended up giving it away.

Note: Pure speculation on my part, but the reason for the limitation may be related to the fact that the DVAP originally was designed to enable DPLUS (REF) repeater administrators to remotely monitor their repeaters, rather than for end users playing around with digital voice more broadly.

More info: DVAPTool⩘ .

⊙ DV4mini Control Center and DV4home firmware

Created by Uli Altvater, AG0X/DH6SAB, and Torsten Schultze, DG1HT.

For running the DV4mini and DV4home. I found these two apps pretty clunky when I tried using them in late 2016. I particularly disliked that the DV4home is set up to try to push you into using DMR+ and to make it challenging to use DMR-MARC or BrandMeister. Thumbs down.

More info: DV4mini Control Center and DV4home firmware⩘ .

⊙ KB5RAB RPi Image

Created by Russell, KB5RAB.

I haven't tried and don't know much about this actively maintained image, but it looks like a kitchen sink full of software to run many aspects of Digital Voice on a Raspberry Pi. "Image supports DMR, DSTAR and Fusion and each mode can be enabled as desired." I'm guessing it's aimed at real tinkerers because you end up with all this software loaded onto Raspbian Jessie, and it's up to you to install and configure each of the various components you want to use. Includes:

More info: KB5RAB RPi Image⩘ .

3) Stay safe

I recommend staying away from apps that aren't being actively maintained, updated, and supported. Hotspots connect your personal network to the internet, and given the state of (in)security on the internet these days, it's really helpful if the apps they use is being kept current by actively involved developers.

Probably the most important and basic thing you can do to protect yourself is to update the software you use to its newest version. That means using an updated version of whatever operating system you're using, and updating all your apps and software. It also means updating the firmware on your router, connected devices, and any other gadgets you use that can connect to the internet.
The Motherboard Guide to Not Getting Hacked⩘ , Nov 2017

Also, wherever possible, use unique, difficult-to-guess passwords!

4) Beware of unauthorized clones

The MMDVM_HS_Hat is an open source project. The design was released by the creators under a Creative Commons Attribution-NonCommercial-ShareAlike (CC-BY-NC-SA) license. As you can tell from the name, this license explicitly does not allow commercial use. From the MMDVM_HS Hat GitHub page⩘ :

This project is released under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (CC-BY-NC-SA 3.0, https://creativecommons.org/licenses/by-nc-sa/3.0/) license. You may edit and share it as you like, as long as credit is given and the license is not changed. You can build as many boards for you and your friends as you like and you can even sell it to them to cover your costs, however it is strictly forbidden to turn this into a commercial product! You are not allowed to build and sell these boards for profit!

The creators of the board released their design this way so that other hams could use the design to make these boards for their personal use. Basically, they gave a gift to all of us in the ham community.

Unfortunately, there are unauthorized MMDVM_HS_Hat clones, like the JumboSPOT, made in China and sold by various vendors on eBay as well as by other sellers who disguise them with names like J-Hat.

Unauthorized clone

The producers and vendors of these boards are abusing the terms of the Creative Commons license; basically, they are ripping off the gift. In addition, from comments I've read online, the clone boards are likely not made with the same level of quality and care as the originals, and appear to be not well supported.

In my opinion, it's always best to directly support the hams contributing to our hobby by pouring their creativity, intelligence, and passion into making these innovative advances in amateur radio.

For more info, see: How to Identify a Genuine #MMDVM_HS_Hat⩘ . Thanks also to Ron, VE1AIC, who explains all of this clearly in his 2018-02-04 blog post⩘ .

5) A shout out to Jonathan Naylor

I'm a digital voice end user with a relatively low level of technical competence; however, I love to understand things as much as I can, which has led me to do a bunch of research into all of the digital voice products I use, especially hotspot hardware and apps. As I've been exploring this, one name keeps popping up: Jonathan Naylor, G4KLX.

Jonathan operates in a technical stratosphere I don't understand much about. Yet I do know that he has been creating important digital voice-related solutions for years, which he makes freely available to the community of hams who are innovating in this playground and helping to make amateur digital voice radio so exciting.

Here's what Pi-Star's Andy Taylor says about this:

There are some more special people who we all owe a debt of gratitude for their willingness to release their software for free. Jonathan Naylor (G4KLX) for his most excellent DStarRepeater, ircDDBGateway suite, and more recently MMDVMHost and DMRGateway. These applications form the core of what makes Pi-Star what it is, and without these excellent applications Digital Voice for Amateurs would be an entirely different and barren landscape.

Even though I don't understand much of Jonathan's work, I know it helps further digital voice radio for all of us. For that, a big thanks!

Here's a video of one of Jonathan's talks: MMDVM⩘ , 2017. For more info, see: GitHub g4klx⩘  and MMDVM group⩘ .

6) Zooming around with ZUMspot

For fun, I decided to make some hotspot cases out of some mahogany thinwood I had. I ended up building five different cases. Here are the two winners.

Shack hotspot

The setup for my shack is a ZUMspot mounted on a RPi 3B with a Pi-UpTimeUPS for uninterrupted power. The Alchemy Power Pi-UpTimeUPS takes two type 18650 3.7V batteries. I use EBL 3000 mAh capacity batteries.

ZUMspot connected to RPi3 and Pi-UpTimeUPS

Since Pi-Star can run headless, the hotspot really doesn't need any external ports except for power in. It basically can be a black (or mahogany) box with an antenna, on/off switches between the external power port and the UPS and between the UPS and the RPi, and, optionally, a display screen. So I made a simple rectangular box case: 4.5″ wide × 4.7″ deep × 3.5″ high, with the width determined by the display.

ZUMspot hotspot v2

To reduce the footprint of the display, I soldered wires directly to its back rather than using the connector that plugs into its side. Since I'm using those same soldered wires to connect the display directly to my PC for programming via a USB to TTL UART CH340 Serial Converter, I don't need to leave space (or cut a slot) for inserting a microSD card into the display. That means I can incorporate a 3.5″ display in roughly the same space needed for the width of the boards.

Back of Nextion display showing wiring

I added a plexiglass base to the stack of boards, and the resulting stack determined the height of the case. The boards slide into the case and are held in place by a rectangle of wood that anchors the plexiglass base. Then the case piece holding the display screws into that front opening.

The stack of boards anchored inside the box

The cables and switches determined the depth of the box. Here you can see them crammed into the remaining space. The case piece with the switches exposed screws into the back opening.

The stack of boards anchored inside the box

For the on/off switches, the best option I could find is the LoveRPi Power Switch, which includes a green status LED showing when it's on (important in a black box scenario). It includes three different colored rubber covers for the switch.

LoveRPi Power Switch

The power switches and the single port, the micro-USB power input, are located on the back of the case. The cable with the green switch controls power between the UPS and RPi. The cable with the black switch controls power between the input port it provides and the UPS.

The back of the box with the power switches

(If I were to do this again, I'd use a short micro-USB male-to-female extension cable to provide the input port instead of the cable with the black switch, because I never turn that switch off.)

Mobile hotspot

"Simplicity is the key to brilliance." – Dieter Rams

The design for my mobile hotspot was influenced by two things, a desire for simplicity, and hunger for battery operating time. I decided on a minimalist design: just the ZUMspot + RPi Zero W, powered by a ruggedized RAVPower 10050 mAh portable charger, which has a similar footprint.

Minimalist ZUMspot mobile hotspot RAVPower 10050 mAh portable charger

I added a right-angled micro-USB adapter to make plugging in easier (it aligns better with the port on the charger), as well as to reduce wear and tear on the RPi's micro-USB port. The small mahogany case fits nicely on top of the battery, which gives me a full day's capacity. I used a sophisticated solution to attach them together: two rubber bands from some broccoli we bought.

ZUMspot hotspot v4 in action with D-STAR and DMR

Size comparison

                 Width  Depth  Height
Shack hotspot:    4.5″ × 4.7″ × 3.5″
Mobile hotspot:   3.2″ × 2.5″ × 1.1″
External battery: 4.6″ × 2.8″ × 0.9″
Deck of cards:    3.6″ × 2.6″ × 0.7″

7) Dissecting a hotspot case

I thought it might be fun to show the inside of the case I built for my MMDVM_HS Hat-based mobile hotspot, which is a bit of a puzzle case. One thing that came out nicely is the opening I cut by hand for the right-angled micro-USB adapter, which came out perfectly snug, so the adapter just sits in there without any glue.

The components of my MMDVM_HS Hat-based mobile hotspot case

The modem board and RPi Zero W fit in and slide onto the adapter. Then a filler piece drops in. It has a notch cut out at the bottom to allow for air flow up through the holes drilled in the bottom of the case. It's purpose is to hold the adapter in place when I plug in a cable so that there's no stress on the RPi, and it also contributes to keeping the modem board and RPi from moving around.

The hotspot board fitted into the case

The modem board and RPi have standoff feet as well as tops. Once the case top is screwed on, those keep the hotspot from moving up and down. A little piece slips in behind the standoff tops on the long side of the hotspot, which prevents it from moving from side to side. Finally, another piece slips in behind the hotspot's end, and that keeps the hotspot from moving from end to end, and also holds the adapter filler piece in place. Once the top is screwed in, everything is nice and snug with no internal movement, which is important for a mobile hotspot.

All the internal pieces in place

Pi-Star ≫

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