|Subject:||Loops for mobile operating was Re: [TowerTalk] bandwidth vs efficiency|
|From:||Jim Lux <email@example.com>|
|Date:||Tue, 08 Jun 2004 10:55:25 -0700|
At 01:33 PM 6/8/2004 -0400, Tom Rauch wrote:
> >Let's submerge our screwdriver mobile antennas in a cryogenic > >container. An additional advantage would be that no bugs would nest > >in there! > > > >73, > > > > George T. Daughters, K6GT > reducing the loss in the coil will make the bandwidth narrower. You run > into this when you contemplate making high efficiency compact loops. Sure,
There are some commercial mfrs (in Australia, land of pervasive HF mobile) of compact loops that look much like a luggage rack, and there are some journal papers on turning the whole vehicle + a big whip into a fairly large loop. (coupling to the "A-pillar" of the vehicle, with a transformer)
A loop is going to couple to the surroundings, just as a dipole/monopole would, but the coupling mechanism might be different, and the dominant loss mechanisms might be different (high H field, low E field with the loop).
I wonder if there's some qualitative statement that could be made about the relative efficiencies of the two. They're both "physically small radiators", but very different in some ways.
Is it the "ground loss" that's dominating, or the "vehicle body loss"?
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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