Gathering the Hardware

A WPSD device is a small computer (a Raspberry Pi), an MMDVM modem board on top of it or plugged into it, and a microSD card. You also need a digital radio to talk through it, and a computer or phone with a web browser to set it up.

A Radio

You can use nearly any radio that supports one of these digital modes:

  • DMR

  • D-Star

  • Yaesu System Fusion (YSF/C4FM)

  • P25

  • NXDN

  • M17

  • POCSAG paging (with a pager)

Every mode works equally well through the WPSD device, so choose a radio for your own reasons: what your local repeaters and club use, what your friends have, the price, or the color.

You won’t be transmitting far, so you don’t need much power. Too much power can even overwhelm the modem: use your radio’s lowest setting.

Two common starting points, if you want a suggestion: the Retevis RT3S (DMR, inexpensive) and the Yaesu FT-70DR (System Fusion).

Single Board Computer

WPSD Palisade runs on these Raspberry Pi models:

  • Raspberry Pi Zero 2 W

  • Raspberry Pi 3 (all versions)

  • Raspberry Pi 4

  • Raspberry Pi 5

The image is built and tested for these boards only. Older 32-bit models (Pi 1, Pi 2, Pi Zero, Pi Zero W) and other single board computers can’t run it.

Don’t save money on the power supply. Cheap switching supplies are often electrically noisy, which shows up as poor reception, and many deliver less than their label says. Use one rated for your Raspberry Pi; the official Raspberry Pi supplies are a safe choice. Some people run their WPSD device from a rechargeable battery pack, which avoids power supply noise entirely.

Modem

The modem is an MMDVM board, usually with an ADF7021 radio chip.

Note

MMDVM boards with one ADF7021 radio chip are hotspot boards: they have a single SMA antenna connector or a small ceramic antenna on the board. Boards with two ADF7021 chips are duplex boards, with two antenna connectors: they receive and transmit at the same time, which DMR uses to carry both timeslots. Boards with no radio chip at all are repeater boards, which connect to separate radios and have no antenna connector. WPSD Palisade supports all three.

The modem receives the digital signal from your radio and turns it into data the WPSD device sends over the Internet, and the other way round. It has two main parts: the ADF7021 radio chip (or two), transmitting at very low power (about 0.1 to 0.25 watts), and a small microcontroller running the modem’s firmware.

Modems known to work well with WPSD:

  • ZUMspot GPIO and USB MMDVM boards, and MMDVM-Pi repeater boards

  • DVMega boards and hotspots (from the Netherlands, not the UK)

  • LoneStar (N5BOC) GPIO and USB MMDVM boards

  • BridgeCom Systems SkyBridge hotspots

  • BI7JTA MMDVM boards

  • Repeater Builder STM32-DVM boards

Some modems behave poorly; this article to modem vendors explains the common problems. The WPSD project doesn’t make modems or their firmware, and can’t support a modem’s own peculiarities.

SD Card

A microSD card of 8 GB or more, Class 10 or better. WPSD Palisade stores very little, so a larger card doesn’t help. A card from a known brand lasts longer than a no-name one.

A Computer or Phone

You’ll write the image to the SD card on a computer (Windows, macOS, Linux or ChromeOS). After that, everything is done in a web browser, on a computer, tablet or phone. The dashboard works on a phone, but a larger screen makes setting up easier.