APRS

 While a lot of people generally use voice transmissions on the 2-metre band, another popular mode of communications is APRS, created by the late Bob Bruninga WB4APR in the 1980s, many hams use it solely as a means so they can be tracked however it has uses beyond this, something the creator noted on the main APRS website, something he continued to maintain until he became silent key in 2022.

The system, apart from being used for tracking can also handle basic text messaging, so long as the radio can support it, placing static objects on a map (my iGate does this for two items both over the Internet and over RF), an event run from the United State, APRS Thursday, utilises the text messaging facility to check in to the nets.

Most modern radios by Yaesu, Icom and Kenwood are equipped with APRS, some cheaper Chinese radios like certain AnyTone DMR radios and certain Vero radios are also equipped, radios not equipped with APRS can either use a dedicated data port and TNC (a type of modem basically) or alternatively a smartphone running a suitable app and a cable connecting to the radio via an audio port (which may require activation of VOX to allow transmit so not advised), other options are Bluetooth devices that plug into these radios as well that pair with a smartphone, standalone devices are also available to do this.

Part of the APRS infrastructure are iGates and digipeaters, these operate on the same simplex frequency and are usually operated by an individual, this allows packets received to be sent to the APRS-IS, most commonly using an Internet connection, digipeaters will store and forward anything they receive.

The technical side is that APRS uses AX.25, so anything capable of decoding AX.25 should decode APRS packets, the decode facility for this is built in to the Gqrx SDR software which is part of the GNU Radio suite and commonly used on Linux systems including Raspberry Pi, often with RTL-SDR devices, there are ways of also decoding APRS by feeding the audio into a suitable application, often done on Windows systems.

APRS uses a single frequency depending on where in the world you are (with exceptions), in Region 1 (UK, Europe) this is 144.800MHz, in Region 2 (US, Canada) this is 144.390MHz, satellites including the ISS use 145.825MHz though to use these is like any other satellite operation, you need to know when the satellite is passing, the same apps you would use for voice operation over satellites will work fine for these provided the software knows about it, ground iGates and digipeaters don't usually monitor the satellite frequencies, other countries you should check online for further information as I'm only aware of the US and European frequencies.

Setting up an iGate or digipeater is straight forward and requires a suitable radio, a computer (Raspberry Pi boards are ideal for this) and a suitable means to interface the radio to the computer, the authors of the popular direwolf software have a circuit for interfacing in one of the manuals which I use with my own iGate, the radio doesn't need to be expensive, I use a Leixen VV898 because it was a spare radio I had when I set it up, other options are the Motorola GM3xx radios, specifically the 4 channel radios or some other ex-commercial radio that either has an interface on the back or detachable microphone, provided it is capable of 12.5kHz narrow FM you should be fine.

I have a separate website for my own iGate and I often go out with my Yaesu FT2D, which beacons APRS packets when I leave the house, I used to operate mobile until a car accident (which was the last day I had APRS enabled to beacon on the Yaesu FTM-400 and it, disturbingly, beaconed, right when the accident occurred).

A good service to use to see APRS objects on a map is aprs.fi, this allows you to look up a station by callsign and will show stations that are both using RF and Internet-only, it will also show other interesting items like weather stations and AIS from ships so indeed worth a look, you don't need to be licenced to look at the map but if you want to put anything onto the map you have to hold a valid Amateur radio licence unless it is a weather station which you would do with other means, AIS data is fed in from coastal stations monitoring the maritime band (to transmit that you would need a ship's radio licence, not something I cover here)

If you haven't used APRS before, I recommend trying it at least once, and also have a go at APRS Thursdays, as long as you're in range of an igate or digipeater you should be able to participate, just do a search for APRS Thursday, it runs every Thursday from midnight to 23:59 UTC