RadioBanter - View Single Post - improve S/N for AM car radio by a factor of 2...5...10?

Cecil Moore[_2_] · January 23rd 09, 01:37 PM posted to rec.radio.amateur.antenna

wrote:
I don't see how you could be receiving the magnetic
field if say you are 150 miles away from the station.

The same (flawed) argument could be used for the
electric field. :-)

Every photon contains both an electric field and
a magnetic field. The physical particles associated
with all electric, magnetic, and electromagnetic
fields are photons. It is simplistic thinking to
try to separate these phenomena which were unified
a long time ago.

Any receiving antenna is receiving electromagnetic
waves (photons). The ratio of the electric field
to the magnetic field is constant for free space.
A wire antenna in free space responds to the electric
field and extracts power resulting in less power being
available to both electric and magnetic fields. A ferrite
rod antenna responds to the magnetic field and extracts
power resulting in less power being available to both
electric and magnetic fields. The plane wave E-field and
H-field are normal to each other and polarized by
the plane wave transmitting antenna.

The power in an EM wave is ExH and the ratio of E/H
is constant for a constant medium. If energy is
extracted from either the E-field or H-field, the
magnitude of both fields are reduced by the same
percentage.

At the California 75m mobile shootouts that I attended,
the receiving antenna was a horizontal ferrite rod. It
was relatively impervious to the effects of non-metallic
objects in its vicinity, e.g. human bodies. It was
receiving the vertically polarized ground wave at a
distance of about 10WL from the transmitting antenna.

From W8JI web page..
"Acceleration of charges causes a very unique force
on other charges in the Universe. We call this effect
electromagnetic radiation. It is a totally different effect,
and it is independent of induction fields. This is the only
effect or force that works to move charges at a very
large distance, and it cannot be created by mixing
induction fields. "

W8JI doesn't seem to realize that "induction fields" have
been unified into the field of "electromagnetism". Any
difference between an electric field, a magnetic field,
and an electromagnetic field is purely quantitative, not
qualitative as W8JI implies.

I'm not saying that a coaxial loop is a "magnetic" antenna.
I am saying that antennas do exist which respond primarily
to the magnetic field and a ferrite rod antenna is one
obvious example proven by rotating the ferrite rod in the
presence of a vertically polarized signal. Note the
polarization of a radiated plane wave is referenced to
the E-field, not the H-field.
--
73, Cecil http://www.w5dxp.com