The TH-D75A is the easiest APRS setup in my whole lineup, and it is not close. Built-in GPS, a dedicated APRS mode button, dual-band RX so you can watch a data frequency and talk on another, and a real screen to read packets on. No Digirig, no laptop, no companion app required. Here is how I get it running from a fresh radio.
Confirm GPS Lock First
Before touching APRS settings, get outside or near a window and let the internal GPS acquire a fix. Press the GPS key and watch for satellite bars and a valid lat/long on screen. Nothing else in this setup matters if the radio does not know where it is. Indoors, especially near metal roofing or deep in a house, this can take a while or fail entirely.
Set Your Callsign and SSID
In the APRS menu, set MY CALLSIGN to your callsign with an appropriate SSID. I run KZ7K-7 on this radio since it is my handheld. If you also run a mobile or home station on APRS, keep SSIDs distinct so other stations and mapping sites like aprs.fi can tell your devices apart at a glance.
Dial In Frequency and TX Delay
North America runs APRS on 144.390 MHz. Set that as your APRS frequency in the radio, separate from your voice VFO, since the TH-D75A can monitor APRS and operate voice on the other band simultaneously. Leave TX delay at the default unless you are keying into a busy digipeater and packets are getting clipped, in which case bump it up slightly.
Choose a Digipeater Path
For most operators WIDE1-1,WIDE2-1 is the right call. It gets you one hop through a fill-in digipeater and one hop through a wide-area digipeater without flooding the network. If I am parked somewhere remote with no nearby digipeater, I will sometimes drop to just WIDE2-1 to reduce congestion, but WIDE1-1,WIDE2-1 is the sane default almost everywhere.
Set Your Beacon Interval
The TH-D75A supports smart beaconing, which adjusts transmit interval based on speed and heading change instead of a flat timer. I leave smart beaconing on for the Jeep or any mobile use since it keeps the track accurate in turns without spamming the frequency on straight highway stretches. For stationary base use, a fixed interval of 10 to 30 minutes is plenty.
Add a Status Message
The radio lets you attach a short status text to your beacon. I keep mine simple, something like a grid square or a short note about what I am doing. This is optional, but it is a nice touch when someone looks you up on aprs.fi and wants context beyond a dot on a map.
Test Before You Trust It
Send a manual beacon and then check aprs.fi from your phone. If your position shows up within a minute or two, you are done. If it does not, check that your GPS actually has a fix, that your frequency matches 144.390, and that a digipeater or IGate is within range of your location. APRS coverage is very regional, and a strong signal with nobody to relay it will not show up online even though the radio did its job correctly.
Related reading: What Is APRS? · Configuring APRS on the AnyTone AT-D878UV II Plus · Setting Up APRS on the AnyTone AT-D578UV III Plus