Richard Clark, KB7QHC wrote:
"In land stations the actual effective height is from 50 to 90% of the
measured height."

If the effective height is 50%, volts at the antenna terminals are no
more than 50% numericcally of the volts per meter in the field strength
when all else is optimum. This could account for Reg`s 2 to 1
discrepancy. I wonder what the speculations of Reg and his Icelandic
correspondent are? Do they have a formula to predict effective height?
Does Roy have such a formula? It`s a factor which won`t go away, even
when ignored..

Best regards, Richard Harrison, KB5WZI

On Wed, 21 Dec 2005 07:22:58 -0600, (Richard
Harrison) wrote:
Does Roy have such a formula? It`s a factor which won`t go away, even
when ignored..

Hi Richard,

For the NIST half wave field antenna:

Leff = (wl / pi) · tan (pi · len / 2 · pi)

whe

len = (wl / 2) · [1 - (.2257 / (ln(wl / d) -1))]
d = dipole rod diameter, meters

Otherwise, for very short antennas it appears it would be the area
under the curve of the current distribution for the vertical element.
You will undoubtedly run across the formula above, or a variant, in
your copy of Kraus.

73's
Richard Clark, KB7QHC