I thought I’d take a few minutes and talk about something I’ve been tinkering with lately…APRS. I don’t have a radio with native APRS functionality. For a little while I’ve been playing around with a 5w Chinesium handheld and an interface cable that attaches to my phone using an app called APRSdroid. Very cool little app. However, with the HH radio, using it in my vehicle is just about impossible. So I got together with a buddy last night and we built a proof-of-concept interface cable for my mobile radio.
It looks ugly…just like a proof-of-concept is supposed to. Soon, I’ll be putting together a more robust version.
Essentially, I’m using the Cat-5 mic input to get audio from my phone to the radio, and the headphone jack for the return trip allowing two way data communication.
This is a very under-used resource for people who travel off the beaten path and out of cell range. I can use it on the trail to track my wanderings and anyone call follow me by logging into APRS.fi and searching my callsign. I can use it for two way SMS text communication for letting the wife know I’m not dead…or more importantly for texting for help if my situation has gone south. Vocal ham is great if there’s a) someone listening and b) if they care enough to help. Using APRS SMS, I can text anyone’s cell phone anywhere and provide them my exact co-ordinates. I could also set it up to beacon a more general distress call, but again, at the mercy of anyone paying attention.
For me, this is a very viable alternative to the expensive satellite options (inReach, SPOT, etc). No monthy service fees and no additional expensive equipment to buy. At least in the PNW, with the density of digipeaters and Igates, I would be very hard pressed not to be able to reach one if I needed to.
The pictures show my cable, how it hooks to my radio and phone, and the various displays I have access to using the APRSdroid app.
I have the Kenwood 710G dual-bander in the truck and have 1 channel set up for APRS. Any time I have the radio on, it’s pinging out to the world. Also set it up with SMSGTE so I can send and receive txts through it (but boy is it clunky). Probably need to set that up again to make sure I’m still stored in their database.
Depending on areas, it can be real hit or miss on reaching a digipeater that will reach a gateway to APRS.FI. Around here it is pretty well covered, with terrain constraints to be dealt with always. There’s a lot of areas that have been surprising to me with lack of coverage (i.e. the eastern Sierra).
Haven’t devised a good solution to output to a course plotter to see others in the area, there was a specific Garmin (Nuvi 350) that worked pretty good as it wouldn’t retain the beacon info on the screen. (it would refresh when a new position was reported, rather than just filling the screen with dots). Of course whether something like that or APRSDroid, it comes down to a way to get the info out of the radio and I just haven’t spent enough cranial intercourse on devising an overly complex solution.
From the December/Christmas-Solstice Run. Bounced off of both Mission and Badger, then onto various gateways in BC, Eastern OR, and even back over the Cascade to Baldi (On APRS.FI, you can search by date per call sign, and tehn each point will show how it was relayed, pretty cool)
Elk Summit Lookout area near Elk City, ID, was transmitting through the whole area but only picked up at the top📷
Texting through APRSdroid is as easy as using any other messaging app with the exception of there not being an address book. You have to type in the number each time. But I’ve set up a set of aliases and SSIDs for people I would most likely ever text so that makes it pretty easy.
Are you beaconing at full power in those regions you’ve had limited success?
That assumes you have the APRSdroid device connected to the radio, that’s where I haven’t progressed. I do have alias stored in the radio, but using the number keys on the mic is a pain
Yes, full power. If you look at the APRS.FI map you can see there isn’t much, if any traffic in some of those areas. Maybe aircraft that can hit repeaters pretty easily, but that’s about it. Look around Tonopah, there’s some weather stations and a couple of repeaters but no APRS traffic, and no gateways
John, how do you like the D710? I’m still new to ham, I have progressed from stage one (Baofeng in the vehicle) to stage two (Baofeng with external antenna). I’m looking for a dual band mobile with remote head, which looks to be in the $300+ range and I’m thinking I might as well add another couple of Benjamins to get the integrated APRS.
In your opinion, is it worth getting a TM-D710GA instead of a TM-V71A?
From what I’ve read, the D710 TNC doesn’t support sending text from APRSDroid, only receive. Not sure if it’s a big deal for the 60 or so characters you can send in a message over APRS.
Since the proof of concept was a limited success, I’ve set about making a more robust version. I’m using a j box for all the connections this time instead of hard wiring them so I can easily tinker with it in the future. Discovery 1 is that the TRRS connectors I bought are absolutely hideous to work with. Even with 22awg wire in my cable it’s too crowded in there. Can’t get it to not short out. Said screw it and ordered a TRRS pigtail today. Part was $2 and shipping was 7…so I bought 3 to make it worth my while haha.
The D710G is a great radio, more than I will ever utilize (or probably understand). Having the TNC and GPS built in is great but your probably paying a premium over what you could do with separate devices as you need them. The simplicity was worth it to me, still need to figure out an elegant way to get a serial connection out into APRSdroid so I can use the phone as an interface/chart plotter.
Would like to see a group with this capability and being able to track others locations on trails, etc. Jump off to a different frequency so you don’t get any other transmitter adding clutter.
I mounted the head unit in the overhead, would need to route more cables up and down to get a serial connection to it or see if I could cram a bluetooth/serial adapter up there too. Great, I have enough unfinished projects…