Part of our Getting On The Air: Modes, Operations, and Making Contacts guide.
A personal DMR hotspot is one of the best upgrades you can make to your digital radio life. It turns a low-power handheld into a gateway to the whole world of talkgroups, and it fits in your pocket. The build isn’t hard, but there are a handful of forks in the road where people get stuck: which software to run, how to get a DMR ID, whether to buy a simplex or duplex board, and how to actually get the radio talking to the thing. Let’s walk through all of it.
What you’ll need
- A Raspberry Pi. A Pi Zero 2 W is plenty for a single-user hotspot and sips power. A Pi 3 or Pi 4 works fine too and gives you a bit more headroom. Even an older Pi Zero W will run it, just slower.
- An MMDVM hotspot hat. This is the radio board that stacks on the Pi’s GPIO pins. More on simplex versus duplex below.
- A microSD card. 16 GB is more than enough. A decent quality card matters more than size.
- Power supply and a case. A clean 5V supply keeps things stable. Many hats ship with an antenna and an OLED screen.
- A DMR-capable radio and, critically, your DMR ID (we’ll get to that).
Getting your DMR ID (and why mine took forever)
Before your hotspot will do anything useful, you need a DMR ID. This is a unique number tied to your callsign that identifies you on the DMR networks. You only get one, it’s free, and it stays with you.
You register for it at radioid.net. The process is straightforward on paper: create an account, submit your callsign, and upload proof that you hold a valid amateur license (typically a copy of your license or a screenshot of your entry in the official database). Then you wait for a human to approve it.
And here’s the honest part: that wait can be maddening. Mine took what felt like forever. Approvals are done by volunteers, so turnaround swings anywhere from a few hours to a week or more depending on the backlog and how clean your submission is. A few things that will save you grief:
- Upload a clear, legible license document. Blurry or cropped images are the number one reason submissions get bounced to the back of the line.
- Make sure your name and callsign match your license exactly. Mismatches trigger manual review and delays.
- Submit once and wait. Resubmitting or emailing repeatedly doesn’t speed things up and can reset your place in the queue.
- Register early. Do this the moment you decide you want a hotspot, not the night you finish the build. Then the ID is waiting for you instead of the other way around.
Once approved, you’ll get a 7-digit ID. That number goes into both your radio’s configuration and your hotspot’s configuration. Without it, nothing routes.
Simplex hat vs duplex hat: which board do you actually need?
This is the decision that confuses the most first-time builders, so let’s make it simple. The MMDVM hat is the piece that actually transmits and receives RF, and it comes in two flavors.
Simplex hat
A simplex hotspot uses a single frequency for both transmit and receive, and it has one radio module. It can’t listen and talk at the same instant; it alternates, just like a walkie-talkie. For a single operator using one handheld nearby, this is completely fine and it’s what most people should buy. It’s cheaper, smaller, lower power, and does everything a personal hotspot needs to do.
The one quirk: because it’s the same frequency both ways, your radio and the hotspot are configured with the same frequency for TX and RX. That trips people up, so remember it.
Duplex hat
A duplex hotspot has two radio modules and uses a separate transmit and receive frequency, exactly like a real repeater. That lets it handle two timeslots properly and behave much more like the infrastructure DMR was designed around. The practical benefits show up when you want to monitor two talkgroups on separate timeslots at once, or when multiple people are using the same hotspot.
The trade-offs are that a duplex board costs more, draws a bit more power, is slightly larger, and requires you to configure a TX and an RX frequency with proper split. For a single user with one radio, you generally won’t notice the difference in day-to-day use, which is why the simplex board is the usual recommendation.
Short version: get a simplex hat unless you specifically want dual-timeslot operation or multi-user support, in which case go duplex.
The software: Pi-Star vs WPSD
Both Pi-Star and WPSD are complete hotspot operating systems built around the MMDVMHost software. Both flash to your SD card, both give you a web dashboard, and both handle DMR, D-STAR, YSF, and the other digital voice modes. They’re close cousins, but they’ve diverged in meaningful ways.
Pi-Star
Pi-Star is the one that built the hobby’s hotspot culture. It’s been around for years, it’s extraordinarily well documented, and nearly every troubleshooting thread and YouTube tutorial you’ll find references it. If you want the path with the most community answers and the most familiar interface, Pi-Star is a safe, proven choice. Its main downside is that active development has slowed considerably, and some newer features and fixes land elsewhere first.
WPSD
WPSD started as a modernized continuation in the same spirit and has become the more actively developed option. It carries a cleaner, more capable dashboard, more frequent updates, better handling of newer hardware, and a range of quality-of-life improvements layered on top of the same underlying MMDVM engine. If you’re building fresh today and want the most current, best-maintained experience, WPSD is well worth choosing. It will feel familiar if you’ve used Pi-Star, just more polished.
Which to pick
For a brand-new build, WPSD is the choice I’d point most people toward because it’s the one being actively improved. If you value the deepest well of existing tutorials and community troubleshooting, or you’re following a specific older guide step by step, Pi-Star still works well. Either way the core concepts, DMR ID, hotspot frequency, talkgroups, are identical, so skills transfer between them. For a deeper personal take after running both, see Pi-Star vs. WPSD.
Flashing and first boot
Whichever software you choose, the setup rhythm is the same:
- Download the image from the project’s site and write it to your microSD card using a tool like Raspberry Pi Imager or balenaEtcher.
- Pre-configure Wi-Fi if the image supports it, so the Pi joins your network on first boot. Otherwise the hotspot broadcasts its own temporary Wi-Fi network that you connect to for initial setup.
- Insert the card, seat the hat firmly on the GPIO pins, attach the antenna, and power up. Give it a few minutes on first boot.
- Open the dashboard in a browser, usually by navigating to the hotspot’s hostname or IP address on your network.
Configuring the hotspot
In the configuration screen you’ll enter the essentials. These are the fields that matter:
- Callsign and DMR ID. Your callsign and that hard-won 7-digit ID from radioid.net.
- Radio/modem type. Select the specific MMDVM hat you bought so the software drives it correctly. Pick simplex or duplex to match your board.
- Frequency. Choose a hotspot frequency in a portion of the 70cm band that’s clear locally and legal for you to use. A common convention is somewhere in the 433 to 434 MHz range, but pick something you know is quiet in your area. On a simplex hotspot, TX and RX are the same frequency.
- DMR master / network. Point it at Brandmeister or TGIF (or both, depending on the software) so it connects to the talkgroup network.
- Enable DMR mode and disable the modes you won’t use to keep things tidy.
Save, let it apply, and the dashboard should show the hotspot connecting to your chosen network.
Connecting your radio to the hotspot
This is where it all comes together. Your radio doesn’t connect to the hotspot over Wi-Fi or Bluetooth; it connects over RF, exactly like talking to any repeater, just at very low power across the room. You program a channel in your radio that matches the hotspot’s settings. Build a DMR channel with these parameters:
- Frequency. Set the radio’s TX and RX to your hotspot’s frequency. On a simplex hotspot, both are the same value. On a duplex hotspot, set the radio’s TX to the hotspot’s RX frequency and the radio’s RX to the hotspot’s TX frequency (they’re mirror images of each other).
- Color Code. This is DMR’s equivalent of a CTCSS tone. It must match the color code set in your hotspot configuration (Color Code 1 is a very common default). If it doesn’t match, the hotspot ignores you.
- Timeslot. On a simplex hotspot, use Timeslot 2 by convention. On a duplex hotspot you can use both slots.
- Talkgroup and Contact. Create a contact for the talkgroup you want (for example, a parrot/echo test group is perfect for confirming everything works) and assign it to the channel.
- Your radio’s DMR ID. Make sure your radio is programmed with the same DMR ID you registered. This identifies you to the network.
Set the radio to low power. The hotspot is often only a few feet away and cranking watts into it does nothing but cause problems and waste battery. A fraction of a watt is plenty.
The first test
Point your radio at the hotspot channel and key up on an echo or parrot talkgroup. That service records your transmission and plays it back, so if you hear your own voice returned, congratulations: your radio is reaching the hotspot, the hotspot is reaching the network, and the whole chain works. Watch the hotspot dashboard while you do this and you’ll see your callsign and ID pop up live, which is a satisfying confirmation that every piece is talking.
From there, add the talkgroups you care about, save them as channels or in a zone, and you’re on the air with the world from a device that fits in your hand. It takes a little patience to set up, and yes, waiting on that DMR ID can test your resolve, but once it’s running it’s one of the most rewarding little projects in the hobby.
Running an AnyTone 878, 890, or BridgeCom Maverick? Your First DMR Codeplug on the AnyTone 878, 890, or BridgeCom Maverick shows how to build that first hotspot channel and test it on Parrot before you build anything else.
Once your hotspot is talking to the network, see Getting Started with DMR for how Brandmeister and TGIF talkgroups actually work, Brandmeister vs. TGIF for a closer comparison of the two networks, and Building Your First DMR Codeplug for programming your radio.