"Reg Edwards" wrote in
:

Error correction :

They need be rotateable only through about 90 (ninety) degrees.

This is to ensure an antenna can always be directed towards maximum
signal even when there are 3 or 4 plastic guy ropes from the top of
the loop which can prevent a complete rotation

Rotation is probably not an option here as it has to sit on an apartment
balcony. There will be some ground clutter, too, from the balcony railing.
But that may not be as debilitating as it looks because the whole business
is 10m up and any currents in the aluminum balcony railing tend to add to
the radiation, though the pattern can become moot.


--
Dave Oldridge+
ICQ 1800667

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.

73's
Richard Clark, KB7QHC

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
--