Michael Coslo wrote:
Roy Lewallen wrote:
Mike Coslo wrote:
On Fri, 14 Mar 2008 11:57:41 -0700, Roy Lewallen wrote:

Richard Harrison wrote:
Build a small scale model that can be tested indoors and report its
characteristics. Antennas are scaleable.
That's more easily said than done. One of the critical characteristics
of a small antenna is loss. And to correctly replicate loss in a scaled
antenna requires scaling the conductivity of the conductors as the
square root of the frequency. To scale to a higher frequency requires
that the conductivity be better than the original. Unless the original
is made from lead and the scale factor moderate, this wouldn't be
possible.

If what I suspect is true, would not the coax also need to be scaled?

Dunno. What do you suspect?

I suspect that the antenna is a tuned circuit on top of coax, and it
needs that coax to radiate effectively. So just scaling the antenna
wouldn't translate to the same results?

Yes. If the coax is radiating, it's part of the antenna. To make an
accurate scale model of the antenna, you have to scale the entire
antenna (that is, every radiating conductor), not just some part of it
which someone has declared to be "The Antenna". In this case, however,
radiating coax isn't likely to be a major fraction of the total loss, so
scaling it in a model probably wouldn't make much difference to the
loss. Its diameter might have a noticeable effect on how much current it
gets and therefore how much it radiates, though, which is an argument in
favor of scaling it.

Roy Lewallen, W7EL