On 1/29/19 5:47 PM, Jeff Liebermann wrote:

Since all the books that you and I have mentioned are from the 1950's
and 60's, and well before small magnetic loop antenna became popular,
I suspect the absence of detailed models and studies are
understandable. Also, the magnetic loop antenna is rather impractical
for anything other than amateur radio use because of the need to
retune the antenna with even the slightest change in frequency. With
commercial use limited or non-existent, I wouldn't expect to see much
funded research into their characteristics.



Hello, and theory (established via experiments with repeatable results)
and applied math don't change, regardless of the decade. The point here
is that AFAIK only hams use the adjective "magnetic" to describe some
sort of property that the antennas covered in those textbooks don't
engender. I've posted before on this subject. The term "magnetic" adds
nothing to describing the geometry or operation of a loop antenna. And
it can add to the confusion if it implies there are additional types of
loops ("electric loops"?) or that a magnet is a component of the antenna.

My own take on all this is that it got started since a closed loop/coil
of wire will experience an induced current when in the presence of a
time-varying magnetic field. No problem here. This is a close-in
(non-radiating) condition such as we would have with coupled loops/coils
inside a power transformer. The RF equivalent would be a having a loop
or straight wire in the near (induction) field of a transmitting antenna.

Now assume that coil/loop is in the radiating (far) field of a
transmitter and performing as a receiving antenna. A distance of
several wavelengths or more will ensure that. In that scenario the loop
is responding to a propagating electromagnetic (EM) field. So is the
loop responding to the magnetic (H) or electric (E) field of an EM wave?
Despite what some folks believe, EM theory says you can't have a
propagating E field without an H field component or vice-versa.
Sincerely, and 73s from N4GGO,

--
J. B. Wood e-mail: