What APRS actually is, and how each digital voice mode gets your position onto the map.
This page assumes you know nothing about APRS. That is a perfectly respectable position — a great many capable operators have gone decades without touching it. But every modern digital voice mode has position reporting built in, most people never turn it on, and the reason is usually that nobody explained the thing plainly.
So: plainly.
APRS is the Automatic Packet Reporting System, created by Bob Bruninga, WB4APR (SK), a research engineer at the US Naval Academy, from the mid-1980s onward. The acronym comes from his own callsign. He died in 2022, and the APRS Foundation was formed shortly after to look after his work.
Bruninga insisted APRS was never meant to be a vehicle-tracking system. He preferred to gloss it as Automatic Presence Reporting System. The point was situational awareness — a live tactical picture of who is out there, where, and what they have to say. Tracking your car is a side effect, not the purpose.
Strip away the jargon and it is four moving parts:
SSID — a number appended to your callsign to say which of your stations this is. N0CALL-7 is conventionally a handheld, -9 a mobile, -1 a digipeater, -10 an IGate. It lets one operator run several trackers without confusion.
Path — how many digipeater hops you are asking for. WIDE1-1,WIDE2-1 is the standard two-hop mobile path. Do not ask for more; long paths clog a shared national channel and are considered bad manners.
APRS is a network, not a mode. The 144.390 packet system is one way onto it — the original way. But the APRS-IS is just a big internet stream of position data, and anything that can inject into it will show up on aprs.fi.
That is what every digital voice mode is doing. None of them use 144.390. None of them use digipeaters. Your position rides inside the digital voice data stream to whatever server your mode connects to — a D-STAR gateway, a BrandMeister master, a Wires-X node — and that server acts as the IGate, pushing your position onto the APRS-IS over the internet.
The radio hop is different in every mode. The destination is identical.
1200 baud packet on 144.390. Needs a TNC (hardware or software) and a GPS. Entirely independent of the internet — it works RF-only, which is precisely why it matters in emergencies. Everything below depends on infrastructure; this does not.
Recall that a D-STAR DV transmission always carries 1200 bps of data alongside your voice, whether you use it or not. Position reporting simply fills some of that.
Turn on GPS in the radio, and your coordinates ride along with every transmission. The gateway strips them out and forwards them to APRS-IS. That is D-PRS, and it is the tidiest implementation of the lot:
The cost is that you only beacon when you talk. A silent D-STAR operator is an invisible one.
This is where people get confused, so read carefully. A Yaesu Fusion radio does APRS two different ways, and they have nothing to do with each other.
1. A built-in analog APRS modem. Yaesu handhelds and mobiles contain a proper 1200/9600 bps APRS TNC. This is old-fashioned analog packet on 144.390, and it is completely unrelated to C4FM digital voice. It needs no digital infrastructure, no reflector, no internet. Fusion radios are, quietly, some of the best standalone APRS radios ever built — and this feature would work identically if C4FM had never been invented.
2. GPS inside the C4FM digital stream. In DN mode, position data rides with your voice as it does in D-STAR. This is what feeds the GM (Group Monitor) display showing which of your group are in range and how far away, and what geotags a snapshot image. Whether it reaches aprs.fi depends on the gateway you are connected through.
If you own a Fusion handheld and have never used APRS, the built-in TNC is the easiest possible place to start. It is standalone and it needs nothing from anybody.
DMR has no always-on data channel, so position gets sent as a discrete data transmission on its own talkgroup — separate from voice.
On BrandMeister, the mechanism is specific:
The clever part: because the position goes out on its own talkgroup as a data call, nobody hears it. No burst of noise in the middle of a QSO, no kerchunk. Compare that with analog APRS, where every beacon is an audible squawk on a shared channel. In this one respect DMR is the best-behaved of the lot.
Two real limitations. Your APRS identity is tied to your DMR ID, so you get as many APRS stations as you have DMR IDs — typically one or two, against the fifteen SSIDs you could run on analog. And this is a BrandMeister feature; other DMR networks may not offer it at all.
All three have location capability defined, but amateur use is thin and gateway support is inconsistent. If you are chasing position reporting, these are not the modes to start with.
| Mode | How position travels | Audible? | Setup effort |
|---|---|---|---|
| Analog APRS | Packet burst on 144.390, via digipeaters and IGates | Yes — a squawk | Moderate; needs a TNC |
| D-STAR (D-PRS) | Inside the voice stream, always. Gateway forwards. | No | Trivial — turn GPS on |
| C4FM (analog TNC) | Ordinary packet on 144.390 — nothing to do with C4FM | Yes | Low — it is built in |
| C4FM (digital) | In the DN data stream; feeds GM and geotagging | No | Low |
| DMR | Data call to a private ID; BrandMeister forwards | No — own talkgroup | High — codeplug + SelfCare |
Honestly? Open aprs.fi and look at your own neighbourhood. Before touching a radio, spend ten minutes watching what is already there — the mobiles moving on the freeway, the weather stations, the digipeaters. The system becomes obvious once you have seen it working.
Then, if you own a Fusion handheld, turn on the built-in APRS TNC and beacon on 144.390. It is standalone, it works without any network, and it will teach you SSIDs and paths in an afternoon.
And if you already run D-STAR, simply switch GPS on. Your position will start appearing every time you talk, and you will have done nothing else at all.