On Fri, 12 May 2006 21:27:35 -0700, Richard Clark
wrote:

On Fri, 12 May 2006 23:26:10 GMT, Dave Oldridge
wrote:

I did some modelling and the difference between 1/2 inch and 2 inch pipe
is really only 6db and I can get nice flexible 1/2 inch pipe.

Hi Dave,

Only 6dB, hmmm? Considering the following:

I'm thinking more on the lines of switching capacitors in and out.

the switch contact resistance will probably swamp out any perceived
efficiency gain achieved by added pipe diameter. You may be lucky and
have them fuse themselves closed - luck could run the other way and
they fuse open.

Even if they don't fuse (gee Richard, its only ~100A RMS loop current
at 10W EIRP (assuming Rr of about 0.001 ohms)... but it will be hard
to achieve such high EIRP), it is some more loss resistance to drive
efficiency even lower.

I wondered about the effectiveness of the switching arrangement given
the very narrow bandwidth of the antenna, it might take a hundred
discrete tuning combinations to effectively cover the 80m / 75m band.

Owen
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