Gathering the bits required for the second iteration of my Pi-based APRS tracker design.
Also got my rx-only IGate off the air while I clear up some licence ambiguity.
Dorji DRA818U + DRA818V + Raspberry Pi Zero W + USB GPS + stacked 2m/70cm yagi + two RF connections + headset + PTT button + small LCD to display position / flip between currently visible sats + USB power bank = fully integrated, automatic doppler-compensating TX+RX FM satellite groundstation. No running out of hands with that lot.
Another few tens of hours required for that! Oh well, best get the parts ordered.
APRS is something I’d heard about but not really ever grasped. With a couple of events coming up where APRS would be helpful, I decided to put the effort in.
Here’s my recipe for a standalone APRS tracker. Note there are tons of different ways to accomplish the same – this is just one way – and my first spin at it too. I’ve got plans to refine this into future iterations.
This interface, from a guy in the states, is brilliant. But it’s very expensive to ship to the UK. However, it’s pretty easy to replicate.
(ignore the bit crossed out in red, you’re not using it)
My old FT-470, which I’m very proud of, has 1x 3.5mm jack, 1x 2.5mm jack, both mono. I had to go back to an old Gopher(!) post to find the details on hooking this up. Fortunately it’s pretty easy.
TX audio comes from the Easy Digi board, through a 0.1uF cap to the mic tip. PTT comes from the Easy Digi PTT pin, through a 2k resistor, also to the mic tip. RX audio comes straight from the rig’s headphone jack to the Easy Digi RX audio in.
OS is Raspbian minimal.
Software is Dire Wolf which is fairly easy to install and configure. More on this in due course. I’ll also put up a script that preps an install with the hardware above.
I had a 4×20 dot matrix LCD display kicking around, so I ended up building this in too – this has ended up more as an APRS “terminal” than a pure tracker. I wrote a basic framebuffer-esque application which handles writes to the screen, and takes updates from other applications via (of all things) local HTTP. All the custom software in this tracker is C# on Mono. I’ve implemented two screens – one with last RX and TX times (for debugging), and another with current position, speed, GPS time, national grid ref, Maidenhead square, and positional accuracy. A closest recent stations screen is an obvious addition.
Here’s Mk 1.
I’m probably going to leave this intact, then for Mk 2, start afresh and iterate a few times as I refine the design.
I’m pleased to say I got word today that I successfully passed the UK Advanced amateur radio examination.
So, formerly 2E1EPQ, and now M0LTE.
Seems as good a time as any to start this new blog.
Thanks particularly to Alison G8ROG, Harry G3NGX, Ray G3SCZ and the guest lecturers, for delivering a really engaging course.
And congratulations, so far at least, to Barry M0SQZ and Dorian M0SLG on their passes – it was a hard exam. Best of luck to those we haven’t heard from yet.
If you’re out there, G0PMF, GOPMG, G1BSN plus others long since out of touch – e.g. Dick and son Richard, thanks for everything in 1995. Little did I know I’d be taking this back up again all these years later. I’ve got a lot to thank you all for – quite probably including at least in part my career. If Google ever brings you to this page, do drop me a line. Best wishes to you all.
Now for that first QSO…