Gathering the Hardware

Here, I’ll review the acquisitions you need to make to create your WPSD system.

A Radio

You may use nearly any digital-capable radio supporting:

  • DMR

  • D-Star

  • Yaesu System Fusion (YSF/C4FM)

  • P25

  • NXDN digital voice modes

  • POCSAG data/paging

There is no practical difference between modes in the functionality of the hotspot. Choose a radio based on your local circumstances, such as what the local repeaters support, your local club preferences, or your favorite color. Any radio that supports one of the above digital modes should work with WPSD.

Because you generally will not be transmitting any distance, higher radio power levels are unnecessary, and sometimes, too much power can overwhelm the modem.

Since people will ask for a recommendation, despite me saying, “Just pick one,” I’ll give two possible choices to get you going:

  • Low price: Retevis RT3S available on Amazon for under $100 shipped (if you are a Prime member.)

  • Lower priced premium brand: Yaesu FT-70DR available on Amazon for under $200 shipped (if you are a Prime member.)

Events such as Black Friday are great times to shop for better prices.

Single Board Computer

SBC hosts and Hotspots supported by WPSD are:

  • Raspberry Pi

    • Zero 2W

    • Models 3, 4, 5.

  • Nano Pi Neo

  • DVMEGA Cast

  • DVMEGE EuroNode

  • ZUMSpot Mini 1.3

  • ZUMSpot Mini 2.4

  • ZUMSpot Elite 3.5

  • ZUMSpot USB Stick

  • BridgeCom SkyBridge MAX/Plus

Any other SBC/device is not supported if I have not listed it.

While not specifically part of the project, I recommend you do not save pennies by purchasing a cheap power supply. These switching power supplies are notoriously noisy, and not all manufacturers are honest about their power levels. Be sure the power supply you use is capable of supporting your SBC. Some people use a rechargeable battery pack, which avoids issues with power supplies.

Modem

Your modem will be an MMDVM modem board with or without an ADF7021 RF chip.

Note

MMDVM modems with the ADF7021 RF chip are called “hotspot boards” and usually have a single SMA antenna connector or an onboard ceramic antenna. MMDVM modems without an RF chip are called “repeater boards;” these have no antenna connections. MMDVM modems with two ADF7021 RF chips are called “duplex boards,” come with two SMA antenna connections, and are typically used for advanced DMR configurations. Some boards with RF capabilities use onboard ceramic antennas, which are a good choice if you do not want to run an external antenna. WPSD supports all three types.

The modem receives the digital signal from your radio and transcodes it to a digital format capable of being sent over the Internet. While your voice is digitally encoded, your radio transmits it as an analog signal. It must be received, encoded, and transmitted across the Internet via the host.

The modem has two primary integrated circuits, or ICs. The first is one (or two) ADF7021 ICs responsible for receiving and transmitting RF. These are low-power devices in the 0.10w - 0.25w range. The second is a microcontroller, similar to the Arduino some of you may be familiar with. This microcontroller has a “firmware “ program loaded, which is responsible for the modem operations.

Modem/hotspot manufacturers known to work well with WPSD are:

  • ZUMSpot GPIO and USB MMDVM Boards and MMDVM-Pi Repeater Boards

  • DVMega (Netherlands; not the UK) Boards & Hotspots / Devices

  • LoneStar N5BOC GPIO and USB MMDVM Boards

  • BridgeCom Systems SkyBridge Hotspots

  • BI7JTA MMDVM Boards

  • Repeater Builder STM32-DVM Boards

Some modems behave poorly within the ecosystem, and be sure to read this article addressed to modem vendors to understand some of the issues. Also, understand that the WPSD project does not provide support for modems, their peculiarities, or develop the binaries for them.

SD Card

I recommend a Class 10 or better SD card of 8GB or more. Since WPSD stores very little on your SD card, a card with more storage may be an unnecessary expense.

A Computer

You will use your computer to create an image on the SD card and for configuration and operations. While it is possible to configure and run WPSD using a tablet or other mobile device, a computer running ChromeOS, Windows, Linux or Mac OS is strongly recommended. Mobile devices have screen limitations that may hinder you from seeing the required menu and status items in the browser.