ZUMspot (MMDVM Digital Hotspot Board)
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| Frequency | UHF simplex link (approx. 430-450 MHz), ~10 mW |
| Power | A digital-voice gateway board, not a station transmitter: it has a ~10 mW UHF transceiver to reach a nearby handheld. It is powered through its host Raspberry Pi. |
| Modes | DMR, D-STAR, System Fusion (YSF), P25, NXDN, POCSAG |
| host | 40-pin GPIO header onto a Raspberry Pi (Zero W/WH, 3 or 4) running Pi-Star. |
| rf | SMA antenna jack; built-in ~10 mW UHF transceiver to your digital handheld. |
| power | Supplied by the host Raspberry Pi (USB). |
| power req | Powered via the host Raspberry Pi's USB supply. |
The de facto standard DIY-class hotspot: a ZUMspot board on a Raspberry Pi Zero running Pi-Star is inexpensive, covers all the common digital modes, and benefits from a huge user community and mature open firmware/software. Kits with a case and OLED make a tidy, customizable hotspot, and Pi-Star's web interface is powerful.
Unlike a standalone openSPOT it requires a Raspberry Pi, an SD card and a Pi-Star setup, so there is more to assemble and configure, and a Pi Zero hotspot is not battery-portable out of the box the way the openSPOT4 is. As a ~10 mW simplex device it is a personal hotspot that needs internet, not a repeater.
The ZUMspot is the classic build-it MMDVM hotspot - cheap, multi-mode and superbly supported by Pi-Star and the ham community. Ideal if you want a flexible, low-cost digital hotspot and do not mind setting up a Raspberry Pi; choose a standalone openSPOT if you want zero assembly.
The ZUMspot is the digital-voice hotspot most hams picture when they think of a 'build-it-yourself' MMDVM hotspot. It is a small board - a Multi-Mode Digital Voice Modem with a roughly 10 mW UHF transceiver - that plugs onto a Raspberry Pi (most commonly a Pi Zero W or WH, though Pi 3/4 work too). Running the community Pi-Star software image, that combination becomes a personal gateway that links a DMR, D-STAR, System Fusion, P25 or NXDN handheld to internet digital networks over your home network.
Its strengths are cost, flexibility and support. The board and a Pi Zero make an inexpensive hotspot, Pi-Star is a mature, powerful web-configured platform with cross-mode tricks like YSF2DMR, and the MMDVM_HS open firmware plus an enormous user community mean help is everywhere. Kits typically include a case and a small OLED display for a tidy, customizable result.
The trade-off versus a standalone unit is setup: you supply and image a Raspberry Pi and SD card and configure Pi-Star, which is more involved than a plug-and-go device, and a Pi-based hotspot is not battery-portable out of the box. As a ~10 mW simplex personal device it also needs internet and is not a repeater. For a low-cost, endlessly tweakable digital hotspot, though, it is the standard. Compare it with the standalone SharkRF openSPOT4 and the digital sound-card interface SignaLink USB.