On Apr 7, 10:48 am, Jim Lux wrote:
Homer J wrote:
Here is a reference to a technical look at short loop antennas from the
1950's by Wheeler.

H. A. Wheeler, "Fundamental Limitations of Small Antennas", Proc. IRE,
vol. 35, pp. 1479-1484

More specifically, the December 1947 issue

From a practical standpoint, this paper is quite useful, although it
mixes effects of the matching network in with the antenna, which the
more rigorous analyses don't. It also doesn't provide any backup for
its assertion of the validity of the "radiansphere" or "radianlength",
hence the equations might not be valid over all possible antennas.

Wheeler's 1975 paper ("Small Antennas", IEEE Trans Ant & Prop, V AP-23,
#4, July 1975, pp462-469) revisits some of the stuff in the earlier
paper and provides more backup and describes the limitations of the
"radian sphere" model (which he defines as the volume within which the
reactive power density is higher than the radiation power density).

Of particular interest to would-be miracle small antenna builders is
that he specifically mentions the problems if there is anything
conductive or magnetic within the empty space oustide the "antenna" but
within the radiansphere (defined as lambda/2pi). The latter paper also
discusses some electrically small antennas (for 15 kHz, lambda=20km)



This is can found in a technical library with access to the IEEE
publications web site (e.g. university or military tech library)

Thane-fer
Homer

"Dave Platt" wrote in message
...

d. If a receiving signal is well polarized in
one direction, say vertically, how much loss
would one expect if the receiving antenna is
oriented such that its preferred polarization is
horiz. ?

The usual figure one sees bandied about is 20 dB.

I've seen it quoted as "up to 30 dB". That's probably under ideal
(or ideally-bad) conditions, though.

20 dB is probably representative of the "polarization purity" of a run
of the mill antenna in its preferred direction.

To be more specific is Wheeler refering to small FULL wave
antennas or smal fractional wave antennas.?
These are very different and one must be absolutely clear with
what Wheeler is dealing with.
My guess is that he is refering to fractional wave antennas
which is very common in the communication field
Regards
Art Unwin KB9mx xg (uk)