The Revival of Packet Radio

 Over the past year, I began exploring practical amateur radio projects and noticed a growing interest in the resurgence of packet radio. Affordable TNC Pi boards for the Raspberry Pi were becoming widely available, along with low cost sound card–based interfaces sold through platforms such as eBay and Amazon. These devices connect directly to the Raspberry Pi’s GPIO header or via USB, making them ideal for experimentation.

A key contributor to this renewed activity is TARPN (Terrestrial Amateur Radio Packet Network), an international group of more than 560 amateur radio operators. TARPN supports the development of packet radio networks and provides extensive documentation for builders. One of their flagship designs is the TARPN NinoTNC, created by Nino, KK4HEJ. This TNC interfaces with a Raspberry Pi or any PC via USB. More information is available through TARPN’s NinoTNC builder resources. The current model, the N9600A, uses through hole components only—no SMD parts—making it accessible for hobbyists.

Supported Modes

The N9600A is a USB‑based 6‑bit‑rate KISS TNC supporting:

• 300‑baud AFSK AX.25 (HF SSB packet)
• 1200‑baud AFSK AX.25 (Bell 202)
• 2400‑baud APSK
• 4800‑baud GFSK
• 9600‑baud GFSK AX.25 (G3RUH)
• Multiple forward‑error‑correction modes for both HF and VHF

The PCB and microcontroller can be purchased online, with remaining components sourced from suppliers such as Mouser or Farnell. TARPN provides a complete bill of materials in spreadsheet format, which can be imported directly into most component distributors’ ordering systems.

The 2400‑baud APSK mode works well with many microphone‑audio transceivers, while 4800‑baud GFSK is suitable for radios that cannot reliably support full 9600‑baud operation. The TNC supports traditional AX.25 for compatibility with legacy systems, as well as IL2P, a modern forward‑error‑correcting link‑layer protocol designed to be more efficient than AX.25. The N9600A presents itself as a 57,600‑baud USB serial device.

Construction and Assembly

This project made an ideal winter build. I chose to assemble two units—one as a backup or potentially for a second node. I ordered the PCB and microcontroller from Hamserve UK for £15 plus shipping. Being a UK‑based supplier, this avoided additional import fees. Hamserve also offers full kits and pre‑assembled units for those who prefer a turnkey solution.

The components for two boards cost approximately £50. Delivery took around five days for the PCB and IC, with components arriving shortly afterward. TARPN provides a detailed, image‑supported assembly guide, including testing procedures. Only basic tools are required; a standard multimeter is sufficient for setup. Working in short evening sessions, I completed both boards over eight nights.

I also 3D‑printed enclosures for the TNCs using freely available STL files.

Radio Interface and Modifications

TARPN maintains a list of compatible radios, including several commercial PMR models that require internal PCB modifications. These radios are readily available on eBay for around £30. As a former Maxon Radio employee, I had access to suitable units. Modification details for the Maxon PM100 can be found here: https://radarc.org/wp-content/uploads/2023/01/MAXON-PM100-PM160-Mods.pdf

Licensing and Node Setup

In the 1980s, packet nodes could be placed on air with minimal administrative effort. Today, however, a Frequency Allocation Certificate (FAC)—formerly a NOV—is required. Applications are submitted through the ETCC website.

UK Node Callsign Structure:

• GB7xxx – Node with mailbox/BBS
• MB7Nxx – Node without mailbox

A “node” refers to the primary station at a location, which may provide services such as chat, mail, BBS, or simple network connectivity.

I applied for an FAC for a packet node under the callsign MB7NEG. Approval arrived within a few days, authorizing operation on 144.950 MHz with an ERP of 25 watts.

The node runs LINBPQ, a packet node software package installed on a non‑graphical version of Raspberry Pi OS. Configuration and monitoring are performed through a web‑based interface.  See photo below of the packet station.

Network Mapping and Activity

With global interest in packet radio increasing, several tools now exist to visualize network activity. One such resource is the UK Packet Radio Network Map, which displays node locations, port information, BBS links, software versions, and RF/IP/UDP interconnections: https://nodes.ukpacketradio.network/packet-network-map.html

Reflections

This project has rekindled many fond memories of operating packet radio in the 1980s—long before the internet, dial‑up modems, and the World Wide Web came along. At that time, packet was widely used across the UK and internationally. Hardware was readily available, and most TNCs connected to PCs via RS‑232 rather than USB, as parallel and serial ports were standard on computers of that era.

Packet radio remains a rewarding and technically engaging part of the amateur radio hobby.

Paul Phillips, G7KBR