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,


--
J. B. Wood e-mail:

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

On 08/24/2016 01:12 PM, rickman wrote:


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


Hello, and before we get too far afield, I submit that well-respected
EM/Antenna theory textbooks (e.g. those by Jackson, Stratton,
Kraus,Jasik, Terman) don't use the term "magnetic loop antenna" just as
they don't use "electric dipole" antenna". EEs who design antennas
don't either. Hams seem to coin their own terms but not always for
valid theoretical reasons IMO. EM theory says if we make the area of a
single loop of conductor carrying uniform current very small then it can
be considered to function as a "magnetic dipole". But EM texts would
call this a small loop vice magnetic loop antenna. Likewise we consider
an "electric dipole" to be a straight conductor of very small length
(compared to a wavelength) carrying uniform current.

Finally, it's not my intent to imply one has to have an EE degree to
enjoy ham radio and build and experiment with various types of antennae.
Just like you don't have to understand all the nuances of fluid
dynamics to enjoy sailing or flying an airplane. Sincerely, and 73s
from N4GGO,

--
J. B. Wood e-mail: