MikeW

The 2009 Des Moines Marathon is now behind us and from my perspective we did quite well. The marathon is our largest public service event requiring our most complex planning and our largest number of operators.

My main job this year was APRS tracking, and secondary was recording all of our communications for later review.

We had only 3 trackers this year and 2 receive stations. We tracked the lead elite runner, the lead relay runner and the official end pace of the event. All three trackers were motorcycle based, the bikes and riders were marathon volunteers and not amateur operators, but they were well organized and technically literate, that made my job much easier.

Each tracker was configured to beacon every 1 minute, in the future I believe we should set the leaders to 30 a second beacon interval. To prevent interference to normal APRS activity, we used the secondary APRS frequency of 144.340 which is completely unused in this region. A temporary digipeater was installed at a local hospital and covered the east end of the course extremely well. Future improvements need to be made in the south west area of the course, they are in the lowest parts of the city and coverage was spotty during most of that area. A second digipeater in that area would give us rock solid coverage of the entire course.

Most of the APRS experimentation in this area passed by several years ago, and as such “surplus” equipment is hard to come by. We put out a request for trackers and not much response was generated. Many people offered tracker parts, a radio here or a TNC there, but very few complete systems.

For the Rx stations, each had a 2M radio and a Kantronics KPC-3 connected to a notebook computer. Command also had a LCD projector displaying the marathon map on the wall for everyone to see. Each laptop used a copy of UI-View32, and the official Course Map was converted, calibrated, and installed on each machine so that the APRS beacons showed up on the course map and could be seen moving around the course in near real-time.

At the end of the day, we ended up using 2 Yaesu VX-8R‘s in Otterbox 9000 cases and Comet SMA-24 antennas along with a Motorola SM-50 VHF mobile with integrated TinyTrack3SMT, Garmin GPS18 and magnetic mount antenna.

The VX-8 with attached GPS fits perfectly in the Otterbox 9000. We used high-capacity batteries to provide the stamina required for 1min beacons and drilled a small hole in the top of the 9000 for the antenna to poke out. The VX-8R may not be as good of a APRS radio as the older Kenwood TH-D7A, but for use as a dedicated tracker it’s much easier to setup and doesn’t require hunting for an endangered species, the RS-232 serial GPS. I look forward to seeing Kenwood’s next APRS HT offering.

The Motorola-based tracker was a disaster. There was no where to mount an magnetic antenna, and thus no ground plane for it to work against once it was zip-tied to handlebars. I suspect this caused RF to seep back into the TT3 and it was pretty much a lost cause after that. After the lead trackers were finished one was quickly reprogrammed to be trail and sent out to replace the SM50.

You think I would have pictures of all the above stuff, but I don’t. By the time I thought about it it was all disassembled and being put away in boxes to be returned to various owners.

Recording events is always pretty low priority, and usually it’s quite easy so delaying it until the last minute is no big deal as I’m setup to record audio from any of my receivers with a couple of button pushes. Using one of the multiple audio outputs on my NCS-3240 I can route audio from any 6 of my connected receivers directly into the soundcard of my PC for recording using X-Corder. The 3240 can also mix audio streams together from those 6 inputs and feed that into the PC, but that is seldom useful as it overlaps of the audio reduce the intelligibility.

Saturday when I finally got around to setting up the audio recording I realized that we use 4 repeaters plus our APRS channel for the marathon. 4 independent audio sources, 1 PC audio input. Even splitting Right and Left stereo (which the 3240 will do) as separate inputs wouldn’t work. X-Corder doesn’t support that, nor did TalkPCR. Only 1 solution apparent solution, throw more hardware at the problem until it goes away!

Recording Station

Need 4 channels of audio recording using 4 PC-Controlled receivers? Well then pull out and dust off 4 computers. I saved these 4 HP ePC 42‘s from the recycler just a few weeks ago. I didn’t know why I’d need them but they were physically small P4 computers with serial ports and Windows XP licenses. 3 of the 4 even worked. The 4th had no RAM, and as I learned yesterday a bad HDD. I’m still not sure I needed them but they did come in really handy. They’re all connected through a standard 4-port PS/2 KVM that cycles it’s input every 5 seconds so you can monitor all 4 connected PCs. It took forever to move audio and serial cables from my normal computer and 3240 to each of these individual PCs, but it was effort well spent. I cleaned up, labeled and untangled quite a bit of wiring in the process. I am, however,  not looking forward to putting it all back the way it was. I’ve been considering consolidation of my receiver collection for some time, replacing many of my base station receivers with 2 Icom R-2500′s. The Icom PCR-1000′s (2) and PCR-100′s (2) that I used for the marathon have served me well for many years, but maybe now’s a good time to look into replacing them and downsizing the number of radios on that side of the shack. The newer 2500 series have multiple simultaneous VFOs and are capable of APCO25 and D-Star demodulation.

Since I had to configure 4 separate recorders, it’s only appropriate that 1 of them was not correct. I forgot to enable the vox logic on 1 system so it recorded several hours straight regardless of activity.

APRS data was recorded at my home station via UI-View’s logging function. In theory I will be able to play back the data stream and watch the vehicles move around the course. I’m not sure it’s very useful, but it was trivial to setup and may be useful for future ARES demonstrations.

Hopefully next year we’ll be able to acquire more tracker units and outfit more vehicles so we can gather a more complete picture of what is going on. About two days before the marathon I realized I’m pretty sure I could intergrate D-Star position reports into this closed system as well and we could easily have marathon official-shadow operators on a voice channel with realtime updates as we talk to them all feeding into the same UI-View map. I’ll probably play with that a bit over the winter, it would involve running my own APRS network server with data feeding in from both  a D-Star hotspot receiver as well as UI-View sending it the stream from the trackers, but would be a nice tool for us to have in the box.