On 2/22/2010 8:54 AM, Richard Fry wrote:
On Feb 22, 5:51 am, Richard Fry wrote:

The loop antennas suggested by others may work well, as they are
vertically polarized for the E-field (as is the loopstick of a typical
consumer-type AM broadcast receiver).

To correct myself, loopsticks respond to the magnetic field of an EM
wave -- which, for vertical polarization, lie in the horizontal plane.

Hello, and this is a common misunderstanding, which may owe to the fact
of the response of a receiving antenna in a near (induction) field of a
transmitting antenna. In the far field (several wavelengths or greater)
from the transmitting antenna the receiving antenna responds to the
propagated electromagnetic field. Now, how a particular antenna is
oriented wrt this EM field will determine its ability to extract a given
amount of available power from the incident EM wave. One can of course
think of the action of loops or dipoles in the far field as per
Richard's statement but that sidesteps the underlying physics. Sincerely,


--
John Wood (Code 5520) e-mail:

Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337