Amateur Radio Goes High Tech?

By George Ewing, And Dave Lundy DMA® SIG Members

At our April 1st meeting we had the pleasure of seeing what might be the largest Crystal Radio set built. Bruce Lundy KA8EDE & Ed Garner WR8A demonstrated their 'high tech' versions of the crystal radios a lot of us played with as children. See Bruce's web page for more details http://www.gemair.com/~blundy/xtal-set.shtml

My brother Bruce (KA8EDE) has been quite interested in amateur radio for about as long as I have been interested in personal computers. Although Bruce does own a PC, he uses it almost exclusively for e-mail and web browsing. My experience and interest with radio, except for my four years of repairing radios and transmitters in the Air Force, has been mostly restricted to listening to commercial and public radio broadcasts. I occasionally help him raise or lower an antenna, and designed a digital keyer and software to program an EPROM for a beacon he built.

When George Ewing announced the start of the DMA(R) Amateur Radio SIG, I thought that would be the perfect way to get Bruce more involved with PCs, but he wasn't interested. And I still wasn't interested in pursuing amateur radio.

Last summer Bruce had an article published in the Xtal Set Society newsletter about a rather unusual crystal set he built after seeing a similar set built by his friend Ed Garner (WR8A). He has occasionally gotten e-mail requests for more info about his design. That eventually led to me creating a web site http://www.gemair.com/~blundy/ for Bruce to show off his projects. I mentioned it to George and he was fascinated, so George asked Bruce if he would demonstrate it at one of the Amateur SIG meetings. Well, Bruce loves to talk about his projects (he IS a ham, after all), so it was arranged for the April 1, 2003 meeting.

In spite of George's considerable promotion of the meeting, attendance was only slightly over a dozen. Since I'd not attended before, I don't know if that was high, low, or average for that SIG. But I do know that those present seemed to be quite interested in the discussion and demonstration by both Bruce and Ed. Bruce started by telling how Ed had been bragging about the excellent selectivity he had been experiencing with a crystal set he had built. Ordinarily, crystal sets are not known for good selectivity (the ability to tune out all stations except the one of interest). With most crystal sets, you will typically hear several stations simultaneously.

Finally, Bruce invited Ed to bring his set over for a demonstration. As soon as Bruce saw it, the secret of its selectivity was evident - high Q coils and adjustable coupling between the input and detector stages to avoid overloading. Bruce enjoys a challenge, so decided to see if he could improve on Ed's design. If you've ever built a crystal set, you probably wound the coil on a toilet paper roll, or maybe a rolled oats box. Not Bruce - his coils are made of 1/4" copper tubing with a 15" diameter and suspended on an 8' long frame of 2x4s!

Both Bruce and Ed discussed several of the design aspects, as well as antenna and ground issues. They agreed that a vertical antenna was most desirable, but how does one string a wire 100' or more vertically? They described their sometimes hilarious attempts at using balloons and kites to suspend an antenna wire, and the difficulties with both methods. (It is extremely important and dangerous to fly a balloon or kite near or into power lines. High voltages can jump many feet as you are providing a ground at the other end of the line.) Bruce unveiled a device he had just recently built to measure the length of wire as it's un-spooled by a kite, and described its construction.

Not content with just a broadcast band crystal set, Bruce has also built a short wave set, and has also been experimenting with an FM crystal set, using slope detection. He displayed both but was unable to receive any FM stations due to the limited antenna available at the meeting.

At our May 6th meeting we will be doing several things:

1. Viewing a video of one of the Amateur radio equipment manufactures factory, Ten-Tec and a demo of their Jupiter transceiver.
2. Encouraging the members that built the Rascal interfaces to bring them in so we can test them and demonstrate the various software to use
3. Talk about the upcoming Hamvention®

We meet the first Tuesday of each month at 119 Valley St 7 PM. For more info send an email to k8dma at dma.org or call George Ewing, WD8NHI at 937-667-3259

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