Saturday, November 28, 2015

Stupid Medium Wave Tricks

So the other night, a ham buddy and I were talking on 2 meter VHF, chewing over some technical issues.  We were using minimum power, about 5 watts, because we live only about a quarter mile from each other.  In the course of things, I mentioned that I'd been playing around on the 160 meter band, he said that his main antenna might be able to tune that low, one thing led to another, and before it was over we were conversing on 153 meters at all of 2.4 wavelengths' distance.  For reference, that's about like using walkie-talkies at the dinner table to ask to pass the salt.  A single Watt on each end was more than enough power.

I guess it was primarily a ground wave path, although both antennas are horizontally polarized.  There is a railroad embankment between our two houses, so line-of-sight isn't generally possible.  OTOH, 160 meter band wavelengths don't really notice a small railroad embankment.

This exercise reminded me of a late Cold War era communication system, the Ground Wave Emergency Network (GWEN; here's the Wikipedia article).  The idea was that, following a nuclear war, the ionosphere might be looking a tad ragged around the edges and it would be great to have a backup system that instead relied on ground waves, hence the name.  Inevitably there were problems, but it is interesting from both a technical and historical footnote perspective.

Back to last Tuesday's exercise.  Yes, 2 meters is a much more suitable band for this sort of thing.  It is good for line-of-sight paths, and doesn't get in your neighbor's Wheaties two states over the way 160 meters can.  But there is a lot to be said for trying "stupid stuff that everybody knows won't work" from time to time.  You never know what you'll find.  In this case, a rock-solid comms link reminiscent of an old Cold War method.  Not really good for anything – if I need to borrow a pair of lead shorts,  I suppose that I could just as easily walk over and ask directly.  But it was technically interesting, and a good time was had by all.

Not In My Back Yard, but not in the usual NIMBY sense.  No, really, I don't have one of these in my back yard.  I only wish that I did.

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