On 8/24/2016 6:43 AM, J.B. Wood wrote:
On 08/23/2016 01:14 PM, rickman wrote:
On 8/23/2016 6:22 AM, J.B. Wood wrote:
On 08/20/2016 04:39 PM, rickman wrote:
I've been studying loop antennas for some time now and I don't recall a
mention of polarization. I would think that a loop antenna mounted
vertically would provide a vertically polarized signal. Is that right?


Finally, someone on the ng said "loop antennas". You can't be a ham
because you didn't say "magnetic loop" ;-). Sincerely, and 73s from
N4GGO,

Not sure what you mean. You are aware that magnetic loops and loops are
not the same thing. Magnetic loops are a subset of loop antennas.


Sorry, guys but it ain't so. It's either a loop (shielded or
unshielded) or something else. This "magnetic" stuff appears to have
originated with hams. A receiving antenna (be it a loop or something
else) in the far (radiated) field of a transmitter samples an incident
electromagnetic (EM) wave. That EM wave has a magnetic and electric
component but you can't have one without the other. J.C. Maxwell (and
others) says so. Anyone, ham or other, who claims that an antenna in
the far (several wavelengths from the transmitter) field "receives" (or
favors) an E-field or an H-field is demonstrating a lack of
understanding of basic electromagnetic theory.

Now, consider two loops, one transmitting and one receiving. If the
receiving loop is in the near field of the radiating loop then it can be
magnetically coupled. In this instance the loop behaves more like a
mutually coupled inductor than an antenna. Perhaps this is where the
"magnetic" loop idea had its genesis. (Just like the immobilizer system
in your motor vehicle that has a loop embedded around the ignition
switch and which couples to the loop in the capsule inside your
transponder key.)

Textbooks on EM and antenna theory do talk about "magnetic" and
"electric" dipoles as theoretical constructs but that's another
discussion. Sincerely, and 73s from N4GGO,

Perhaps you can explain what the shield does on a receiving loop
antenna? Your explanation clearly says an antenna can be magnetic in
the near field. That is what the term means for receiving antennas. At
lower frequencies much interference is in the near field and is electric
rather than magnetic I am told. Think 100 kHz and household appliances.

The term "magnetic" is usually used in context of a transmitting antenna

--

Rick C