Monday, May 16, 2011

May Fox Hunt in the Indian Wells Valley

I planned on using a new program to assist me with my next Foxhunt, APRSIS32. With this program, I can have offline maps, and create overlay objects just for Radio Direction Finding. The program also supports the propagation of this data via APRS, but just to start, I tried it in an offline mode.

Recently, we completed a Tech Class and a few others built a tape measure antenna for themselves. Knowing this, I figured there would be a decent turnout.

Screenshot of APRSIS32 after locating the transmitter. Top Right Triangle was the starting plot. Laptop was the transmitter location.

I met up with the group at the local donut shop with my daughter, she likes to help find it. I prepped my tape measure Yagi and also packed my Arrow in case "somebody" needed to use it. It was 73 degrees with a 15 mph wind, and only gusting to 16 mph as we started. We totaled 6 Hams in 3 chase vehicles for our small area chase. I was joined my a newer ham K6GOH. He was a bit cramped in my small Prius, but we began our chase and he quickly learned how to create the objects for a location projection. After looking at the first two plots for a general area location, I knew I was getting reflections and needed a cleaner plot away from buildings.

We advanced past the projected area and I got myself on top of a small dirt mount, in my classic tactic to get a better plot. With my antenna pointed South East, the South West winds seemed to suddenly increase from a 16 mph gust to 25 mph, and my tape measure Yagi immediately collapsed and my direction finding was opened to a 70 degree area, pretty useless.  We drove to an area closer to the transmitter, and I quickly assembled the 2m side of my Arrow, to get past the wind gusts. Now my radio was flooded with RF, so I activated my built in attenuator and continued to the south end of town. I was thinking it was near the local Wal Mart, or maybe even the local College. The next plot, I eliminated the field near the Wal Mart, and so did another team on the chase, and I got the most accurate plot from the whole chase, directly toward the college. The signal strength was still really strong, so I figured it was in a field about a half mile to the south, not actually at the college. We took a dirt road, and then realized it was closer to the college with the next plot, probably elevated. We found the main road and drove to the large field just below the college on the hill. By the 7th plot, we knew it was at the college for sure, probably on the southern side, or in the field next to the college.

A quick demonstration of Wind destroying a Tape Measure Yagi, by Michael.

Transmitter located, a very good hiding spot.

As we rounded the southern top of the college road, we started looking for potential locations it could be hidden, and to catch a visual of the fox spotter KG6LEW. We found her some what camouflaged in an area with trees as she sat in her chair reading a book. We parked and we started our foot search. My daughter was happy to start running around and started heading in the right direction with my partners help. I followed with my tape measure Yagi, and my Arrow in hand. I hunt with my Yeasu VX-7R, which has an aluminum casing, so I still need an antenna. By this time, I was completely flooded with RF, and I had to pop the coax off, put on another attenuator, and partially re-connect the coax, and I got a direction while I was 75 feet away from the transmitter. Just as I started in that direction, K6GOH located it around 9:42 AM. It was hidden on top of a concrete structure, between two chain link fences, hence all of the reflections because of a double chain link fence, and the wind moving it around shifting the signal a bit.

A car pulled up, and we attempted to hide behind a few trees, even though we were about twice the width of the trees. Nope, students arriving, not operators. We started to get a bit worried because KJ6HBY, a champ of the last few hunts, was not in the area for a good while after we arrived and located the transmitter. It was about 10:15 AM by the time KI6PSX and his sone arrived, and located it around 10:20 AM. They had the same technical difficulties as we did with our tape measure Yagi. The wind actually managed to tear their forward director element. By 10:30 AM, we called out to see if KJ6HBY and his sister KJ6MQM was still chasing. They apparently thought the transmitter was in the field just below the North of the college and then they went all the way around the college campus, before converging on our location to find the transmitter around 10:40 AM.

This was a challenging hunt, with the strong winds, the changing propagation of signals, and deceptively elevated location. We all had a good time, and learned a little more for the next hunt.


KI6PSP + Amanda, my 3 year old daughter
KI6PSX + Michael, his Son

More pictures can be found on the club Facebook page:

1 comment:

  1. Great writeup of the foxhunt and thanks for using APRSIS32. You need to upgrade your version though, as the newest one actually highlights the overlaps of the DF fields as you can see at

    Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32