DigiPi 2.0: Building a Reliable APRS Digipeater & iGate with Low-Cost Hardware

DigiPi 2.0, created by KM6LYW, is a purpose-built Linux distribution designed to simplify the deployment of APRS packet radio digipeaters and iGates. It combines proven packet-radio tooling with sensible defaults, allowing operators to deploy reliable APRS infrastructure using affordable, widely available hardware.

This build focuses on a compact and cost-effective stack: a Raspberry Pi 4, a Baofeng UV-5R Mini, and an AIOC audio interface from NA6D.

Hardware Stack Overview

Raspberry Pi 4
Provides sufficient CPU, I/O bandwidth, and Ethernet performance for 24/7 Dire Wolf operation, APRS-IS connectivity, and logging.

Baofeng UV-5R Mini
While inexpensive, it is fully capable of stable 1200-baud AFSK APRS when properly configured and paired with a quality audio/PTT interface.

NA6D AIOC (All-In-One-Cable)
A CM108-based USB audio interface purpose-built for packet radio. It delivers reliable PTT control, clean audio paths, and eliminates the instability often seen with generic USB sound cards.

Software Architecture

DigiPi 2.0 centers on Dire Wolf, a high-performance software TNC, and integrates:

APRS Digipeater — intelligent RF packet repeating (WIDEn-N control, fill-in behavior)
APRS iGate — RF-to-internet and selective internet-to-RF gating
Systemd services — automatic startup, watchdog behavior, and log rotation
Optional GPSD — precise node location and time discipline

The result is a stable, unattended APRS node suitable for home, community, or emergency-communications use.

Why DigiPi 2.0 Works Well

Fast deployment with minimal manual configuration
Hardware flexibility from HTs to mobile radios
Proven 24/7 stability
Open, inspectable configuration
Active community knowledge base

RF / Audio Signal Flow Diagram (Reference Design)

Logical Flow (left to right):

[APRS RF 144.390 MHz]
          ↓
[Baofeng UV-5R Mini]
  RX Audio (AF)
          ↓
[NA6D AIOC]
  - USB Audio IN
  - USB Audio OUT
  - PTT Control
          ↓
[Raspberry Pi 4]
  DigiPi 2.0
  Dire Wolf TNC
  APRS-IS Client
          ↓
[Internet / APRS-IS]

Transmit Path (reverse direction):

APRS-IS (filtered) or local digipeat packets
Dire Wolf generates AFSK
AIOC keys PTT and injects TX audio
UV-5R Mini transmits on 144.390 MHz

This diagram can be rendered cleanly as an SVG or PNG for your site header or documentation section.

Step-by-Step Build & Configuration Guide

1. Prepare the Raspberry Pi

Flash DigiPi 2.0 image to microSD
Enable SSH
Set hostname (e.g., digipi-w5rtm)
Update system packages

2. Connect Hardware

USB: NA6D AIOC → Raspberry Pi
Radio: AIOC → UV-5R Mini accessory port
Network: Ethernet preferred for iGate reliability

3. Verify Audio & PTT

Confirm CM108 device enumerates correctly
Validate PTT GPIO via AIOC
Set conservative RX/TX audio levels (avoid clipping)

4. Configure Dire Wolf

Callsign and SSID (e.g., W5RTM-10)
Audio device mapping
Channel configuration (1200 AFSK)
Digipeater rules:
- Enable WIDE1-1 fill-in
- Limit WIDE2-1 to prevent flooding

5. Configure iGate

APRS-IS credentials
RF-to-IS gating enabled
IS-to-RF filtering (local objects/messages only)
Position beacon interval (e.g., 30–60 minutes)

6. Radio Configuration (UV-5R Mini)

Frequency: 144.390 MHz
Wide FM
Disable battery saver
VOX off
Stable power source (avoid internal battery for permanent nodes)

7. Test & Harden

Monitor Dire Wolf decode statistics
Verify packets appear on aprs.fi
Enable log rotation
Confirm automatic restart after reboot

Operational Best Practices

Keep TX power minimal (1–5 W)
Use a dedicated VHF antenna with good height
Avoid excessive beaconing
Monitor channel congestion before enabling aggressive digipeating

Summary

DigiPi 2.0 provides a clean, reliable path to deploying an APRS digipeater and iGate using modest hardware. When paired with a Raspberry Pi 4, a Baofeng UV-5R Mini, and the NA6D AIOC, it delivers professional-grade packet performance at hobbyist cost—ideal for strengthening local APRS coverage and contributing to the broader network.