What information are you looking for, capture area or effective height?
Capture area determines how many watts you'll get into a conjugately
matched load connected to the antenna. Effective height determines how
many volts you'll get from an open circuited antenna. The two aren't
directly related. For more information about the two topics, do a
groups.google.com search for postings I've made on those topics in this
newsgroup.

As I've posted here quite a number of times before, the capture area of
a lossless infinitesimally short dipole is very nearly as great as that
of a half wave dipole, in their most favored directions. (The difference
is about 10%, and it's due to the slight pattern shape difference caused
by different current distributions). So except for loss the capture area
of a ferrite rod antenna is within 10% of that of a dipole. But loss in
a ferrite rod antenna will reduce the capture area considerably. If
you're interested in knowing how much power you can get from a ferrite
rod, then, what you need to know is its efficiency, which is a function
of wire length, number of turns, and the antenna feedpoint impedance. I
don't have the time right now to work it out for you.

The effective height of a ferrite rod antenna is approximately:

(2 * pi * mueff * N * A) / lambda

where

mueff = effective relative permeability of the rod (mainly a function
of rod length)
N = number of turns
A = rod cross sectional area
lambda = wavelength

Roy Lewallen, W7EL

John Popelish wrote:
wrote:
Caveat Lector wrote:

Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html


John Popelish wrote:
Have you got a link to a similar site that covers ferrite rod antennas?


I hope this question isn't taken the wrong way, but why would you want
a similar site? That one is terrible for accuracy. The poor fellow who
wrote that page doesn't even know what capture area is.

I meant a site that addressed (correctly, one would hope) that concept
of capture area for rod antennas.

Wouldn't it be better to find a totally different type of site, one
that at least has some technical accuracy?

Okay, I'll take one of those. :-)