Setting up a modern APRS mobile station…

This is a post about my journey in getting a compact portable APRS station going for portable and emergency use…it will be over a few posts as I try a few different methods of implementing my system…enjoy!

APRS stands for “Amateur Packet Reporting System” – APRS has been developed since the late 1980s by Bob Bruninga, (call sign WB4APR), He still maintains the main APRS Web site. The initialism “APRS” was derived from his call sign.

First a brief history of my packet and APRS setups…

I have run packet Radio, off and on since 1995, when I was first licensed as VK5XAW. My first Packet Rig consisted of an Apple Mac Plus, a VK7TM (Sadly, long now a Silent Key) “Pocket Packet” modem I built from a kit, and my first 2m Radio, an Icom IC2GXAT 7watt handheld radio,  plugged into a pole mounted vertical up at about 10m high.

Everyone said it wouldn’t work, but work it did. As far as I knew I was the only one in SA using a Mac for Packet.

The VK7TM kit modem worked
well and the software for the Mac impressed. I had a lot of fun on the VK5TTY bulletin board, and many direct contacts with Stef, VK5HSX.

I went to my first PC, a 486DX100, (!) and then a PK232 – a real proper modem. The 232 soon got relegated to RTTY duties in contests, so I graduated to the PK88 and the MFJ TNC2 clones. I’m sorry to say I can’t even remember the name of the terminal software everyone used to use, written by a French ham? It was a long time ago.

Packet usage began to decline and started to go the way of the Dodo, When it was well and truely elbowed by the newly emerging all singing all dancing APRS.

I believed my first system, from (fuzzy) memory was a MFJ TNC2 clone with a custom ROM, not even a GPS, just  home lat/long entered in to the software as a home station. Quite boring really!

I then moved on to a couple of mobile setups, including a Byonics Tiny Trak3 with a Garmin GPS and Yaesu VX6R 5 Watt handheld, then neat system with an Alnico DR135 Mk111 2M Rig with an Argent Data Systems T2-135 internal modem fitted, with data display and mapping/messaging from a dash mounted Garmin c510 StreetPilot in-car GPS/navigation unit. Luxury!!! The argent data setup used the proprietary Garmin sentences to do the overlays on the Streetpilot.

That system served me well despite its warts. It tended to be erratic with keeping my own path on the GPS map, but did quite a good job of updating other stations. I found the Alnico Radio to be a good performer with bomb proof front end.

I hadn’t run packet for a number of years until recently. My needs with APRS have now changed, and as I’m quite often out doing Park Activations for the WWFF program, so I like the ability to map for two reasons.

A) As proof that I was where I said I was…and

B) Safety. If I’m lost, it should be easy to find me!

After doing a bit of trawling on the ‘net, it seems that there is quite a few options for APRS these days.

Kenwood and Yaesu both seem to have full function units, both high power mobile and Handheld, that are ready to go out of the box – just put your callsign and SSID in and you’re  away. These are a few generations in now, and have matured into 1 box solutions. Both have limitations with the information that can be displayed

As tech has moved on, so has software and by far the best way to display yours and others APRS data is on aprs.fi, a web based app that uses google maps to plot positions and  track stations world wide in a web page.

Tablets have revolutionised mobile computing and this is the way I have chosen to go as a display for my vehicle APRS system that I’m currently putting together.

I have recently acquired a Samsung Galaxy Tab A, as the dash mounted Display for my APRS set up. It is simply Velcro’d to the dash surface, when in use, and removed when not required to reduce the risk of sun/heat damage or theft. It seems to work extremely well. The tablet doesn’t have to be flash, as long as it has an inbuilt GPS, most reasonably recent ones do, it should be suitable. not that you can even use an Android phone at a pinch. 

It is a perfect size for this application, and is a bigger, brighter and clearer display than any currently available out of the box APRS Radio, and can be used as an Android tablet when not pressed in to APRS duty.

The software that makes this all modern day APRS happen is an Android app called APRSDroid. It is a free download from the Google Play store. There is no equivalent iOS app, as iOS lacks support for Bluetooth Serial Port Protocol (SPP). The software supports the following connections…

1.via TCP/IP ( needs an internet connection), 2. via AFSK ( audio in and out using the headphone socket to a Radio, 3. via a Bluetooth to a TNC (like the Mobilinkd TNC) and finally, 4. Kenwood (NMEA waypoint)

At the moment, to get my position on the APRS network, my setup is operational with the Samsung tablet > an ASFK connection via a simple interface> Yaesu FT7800R mobile radio.  APRS RX displays the incoming packets from the 2M Radio, and everything is displayed on the Galaxy tablet in the APRSDroid app. The only disadvantage is that it is not a wireless solution from the Tablet at present, but it’s cheap and it works. The goal is to have say a Pelican style case, with a 2M mobile radio and a Bluetooth capable TNC and all connections ready to go. Just plug it in to some power and an antenna and you’re on APRS, using the Bluetooth connected Tablet as a remote display. A picture tells a thousand words… I have started on the case for the setup, adding an auxilliary USB charging port shown here being tested on the way to help out on a Horus ballon launch with the club…

Until the next instalment on this build, here are a few links to the software and hardware I’m using…

Mobilinkd – http://www.mobilinkd.com/?gclid=CjwKCAjwj4zaBRABEiwA0xwsPwKCAQ68kaig3HeXiN_SCh4bcOryoV-f3G_yN9r2dX8ZgxSLVvXx1RoCXFgQAvD_BwE

APRS.FI – https://aprs.fi/#!lat=-33.86670&lng=151.20000

APRSDroid – https://aprsdroid.org/

Samsung Galaxy Tab A6 – https://www.samsung.com/au/tablets/galaxy-tab-a-7-0-2016-t280/

Andy

VK5LA