Ben's Bits

For a couple of years now the Gopher Amateur Radio club has been provding scanner feeds of the digital APCO-P25 in the Minneapolis/St. Paul metro area to radio enthusiasts around the world through the ScanAmerica.us website (now a part of the RadioReference.com family). In fact, I specifically purchased the fabulous GRE PSR-600 to replace the Radio Shack PRO-2096 because it allowed us to transmit the talkgroup identifier as well as the audio though some hacks attaching the remote control software to the stream broadcast software.

Thanks to K1PGV it looks like there is now some software called ScannerCast which integrates the polling function to get the talkgroup ID for both Uniden and GRE scanners which support it and tag the audio with the talkgroup. This is a much neater solution, if a little bit more limiting in that it doesn't allow for simultaneous remote control of the radio.

This summer I decided to explore a bit more about packet radio. You know, transmitting small amounts of information over amateur radio frequencies at very slow speeds. Prior to the advent of fairly ubiquitous high speed Internet connections this was a popular way for hams to move around information related to their activities. As it turns out the need for a dedicated packet modem (TNC) has gone away and the functionality can now be replaced with software and a sound card. One of my specific interests though was in learning about and improving the APRS system in the Twin Cities which allows people to automatically send GPS position information along with remote weather station packets and a variety of other small pieces of data. As it turns out APRS data can also be sent and received with a soundcard attached to a radio, forgoing the TNC and reducing the barrier to entry.

The primary program for soundcard TNC emulation is a free program called AGWPE and my first task was to learn how to setup and configure it as some of my firends had tried and failed to get it working in the past. Thanks to the great resources on the Internet I came upon the website of KC2RLM which contained excellent instructions for setting up and using the AGWPE program as well as a number of applications which would interact with the software.

Once I had gotten the basic soundcard TNC software up and running the next step was to start experimenting with APRS software. I tried lots of software including the common UI-View32 software but found the easiest to use and most modern software to be AGWTracker, a trialware program by the maker of AGWPE which supports all kinds of map layers such as Google Maps, MapPoint, etc. greatly improving the user experience. Of course, if you want to send updates back to the APRS-IS Internet network you need a password to go along with your callsign. As it turns out the password is a simple hashing algorithm designed just to prevent non-hams for injecting data into the network and is a documented algorithm. You can get your own APRS password or learn more about the algorithm at the APRS Password Generator website.

One of the many misconceptions about the D-STAR digital amateur radio protocol is that it is closed and will prevent tinkering by hobbyists. This turns out to be far from the truth indeed. Last year at the Dayton Hamvention there were several exhibits by D-STAR enthusiasts which included an entirely home brewed D-STAR radio and a home brewed D-STAR repeater controller. Well now someone has built a DV interface adapter which can provide a D-STAR digital voice interface on many existing transceivers. Of course some functionality is missing as there is no ability to change various DV settings from the minimal interface but it proves yet again that there is the possibility for much experimentation with this new digital mode.

On other fronts the OpenDSTAR group has released several software tools which build on existing commercially available repeaters and Internet gateways to extend functionality. Still in the pipe from that group is a USB dongle called the DV Dongle which will allow end users to encode audio in the AMBE format used by D-STAR digital voice for later playback through the repeater or, ostensibly, for live PC to repeater communications. Indeed the home brew spirit of amateur radio is alive and well in the world of digital communications, it just looks different than it has in the past.

I recently found the USRepeaters.com website which contains a listing of many of the amateur radio repeaters in the United States. I actually had a plan at one point to develop a similar PHP/MySQL driven site but simply have way too many other projects going to take on another. That said I do have a few issues with the US Repaters site. First, the site is a mess graphically and navigation leaves a lot ot be desired. The lack of an interface for owners of repaters and/or coordination bodies to make changes, users to search, etc. is also unfortuante. Secondly, the data is copyright instead of being open and freely available. As inexpensive as webhosting is these days and seeing that ham radio has a long tradition of sharing knowledge I am disappointed to see someone attempting to assert control over this factual data. I think a simple ad supported site (not the ads all over approach US Repeaters takes) would be sufficient to support such a directory. If someone out there is interested in working on an open PHP/MySQL repeater directory I would be more than happy to provide web space, bandwidth and my ideas. Contact me if interested.

Many towns, counties and states still using analog based radio communications systems for public safety use Motorola MDC systems which emit a short "chirp" at the beginning or end of a radio transmission. If this is the case in your area you might be interested in the open source WinMDCD software. This software allows you to decode that chirp with a Windows based PC and see data such as date, time, unit ID or whatever else they're transmitting. Note that if you're interested in Motorola radio technology a great resource is BatLabs, in particular the BatBoard which has a great number of people who are extremely knowledgeable about Motorola radios.