The reason you can open a live map at aprs.world or aprs.fi and see a station that beaconed from a forest road three minutes ago is that somewhere within radio range of that station, a volunteer is running an iGate — an Internet gateway that listens to the local RF channel, decodes every APRS packet it hears, and uploads each one to the global APRS-IS backbone in real time.
iGates are pure infrastructure. Most run unattended for years, on a Raspberry Pi tucked behind a router, drawing a few watts of power. They are also the easiest way to give back to the APRS network: if you live in an area where coverage is thin, building one will measurably improve the experience of every mobile operator that passes through.
This guide explains what an iGate actually does, the important distinction between RX-only and RX/TX iGates, the typical hardware and software stack, and the operational considerations that separate a well-behaved iGate from a problem one.
An iGate is two things in one:
What an iGate is not: it is not a digipeater. It does not re-emit packets on the air; that is the digipeater's job. The two roles are often combined on the same hardware (Direwolf will gladly do both at once) but they are conceptually separate. A pure iGate adds value to APRS-IS; a pure digipeater adds value to the local RF network; combined installations add value to both.
This is the first and most important configuration choice you will make.
A RX-only iGate never transmits. It pulls packets off the air and pushes them to APRS-IS. Period. It has no transmitter at all, or if it has one, transmission is disabled in software.
This is by far the most common iGate type, and for good reason:
The downside: RX-only iGates cannot send anything back to the RF side. They cannot deliver messages from APRS-IS down to a local station via the air. They cannot send out the standard "you have a message waiting" prompt. They are pure one-way pumps from RF to Internet.
A RX/TX iGate transmits selectively. The killer feature is message gating (sometimes "messaging IS-to-RF"): if a station that recently beaconed locally has a message waiting for it on APRS-IS, the iGate transmits that message on the local frequency so the addressee's radio can receive it. This is how APRS messaging works end-to-end across the network — your message from a phone in Spain can reach a handheld in Argentina if both stations are in range of cooperating iGates.
RX/TX iGates must be configured carefully:
WIDE1-1 or no path) so it doesn't propagate further than necessary.Most newcomers start with RX-only and add TX capability later once they understand the local channel load.
A working iGate has four hardware pieces:
Almost anything with a USB port and an Ethernet/Wi-Fi connection will run an iGate. Raspberry Pi 3B+ is the typical choice — it draws under 3 watts and runs Direwolf with room to spare. A Pi Zero 2 W works for receive-only. Old laptops, mini PCs, and N100 boxes all work too.
The interface converts the radio's audio out to a signal the Pi can decode. Options:
The single biggest determinant of iGate quality is the antenna. A dual-band whip on a kitchen windowsill will hear stations 10 km away; a 6-dB gain colinear at 10 m of height will hear stations 80 km away. Spend more here than you think you need.
Two open-source projects dominate the iGate world:
Direwolf by John Langner (WB2OSZ) is a modern soft-TNC and APRS station all in one. It demodulates AFSK from a sound card, can act as a KISS TNC for other software, includes a digipeater module, includes an iGate module, and supports IS-to-RF message gating. It is the default recommendation for new builds. Configuration is a single text file; the User Guide is excellent.
aprx by Matti Aarnio (OH2MQK) is a leaner, C-based alternative aimed at always-on infrastructure deployments. It uses less RAM and CPU than Direwolf, which matters on a Pi Zero or a heavily loaded multi-purpose server. It typically pairs with an external KISS TNC (the Mobilinkd, or Direwolf running in TNC-only mode) rather than doing demodulation itself.
For a clean, modern stack, the canonical recipe is: Raspberry Pi 4 running Raspberry Pi OS Lite, Direwolf installed from apt, an RTL-SDR or a DigiRig interface, and a roof-mounted antenna. Total parts cost under USD 150 for a configuration that will run for years.
A minimal /etc/direwolf.conf for a RX-only iGate looks roughly like this:
ADEVICE plughw:1,0
CHANNEL 0
MYCALL TA4OHN-10
IGSERVER rotate.aprs2.net
IGLOGIN TA4OHN-10 12345
PBEACON sendto=IG delay=0:30 every=30 symbol="igate" \
lat=40^30.00N long=032^53.00E comment="aprs.world iGate"
What each line does:
ADEVICE and CHANNEL point to the sound card.MYCALL is the iGate's callsign with an SSID. SSID -10 is the conventional choice for an iGate per SSID convention.IGSERVER points to the APRS-IS rotation pool — see the APRS-IS guide for what that actually resolves to.IGLOGIN is your callsign and your passcode. The passcode is not a secret; it is a deterministic integer derived from your callsign.PBEACON makes the iGate itself appear on the map every 30 minutes so people can see your coverage. Set the symbol to the iGate icon and put a useful comment.Drop the file in place, run sudo systemctl enable --now direwolf, and you are an iGate. Within a few minutes you should appear on aprs.world and aprs.fi.
For RX/TX, you add a PTT line (telling Direwolf how to key the radio), an IGTXVIA line (declaring the path used for outbound messages), and an IGFILTER line (controlling which IS-side traffic Direwolf is allowed to relay out to RF). The Direwolf User Guide chapter on iGating walks through every parameter.
Running an iGate is being part of public infrastructure. The community expects a few things:
-10 for iGates, -2 for digipeaters, -9 for vehicles, -1 for primary station. The full table lives at aprs.org/aprs11/SSIDs.txt.direwolf -t 0 to monitor decode rates.-d flag and config option to flip it.Every packet your iGate decodes is uploaded to APRS-IS, where the APRS-IS network fans it out to everyone subscribed. That includes aprs.world, aprs.fi, findu.com, the APRS World mobile app, and every other tool downstream of APRS-IS. Your iGate is what makes the whole global view possible for the stations within your radio horizon.
Running an iGate is one of the highest-leverage things a single ham can do for the network. A well-sited box with a clean antenna can carry thousands of packets a day from operators who would otherwise be invisible. If your area is thin, please consider building one.