Incoming radio wave polarisation
 

Richard Fry in a private e-mail noted that I had misquoted E. A. Laport
who wrote:
"---it is desirable to employ complementary antennas for transmitting
and receiving."

I typed "complimentary" which means praise or a gift. Surely Laport
meant antennas which work together to perfection which is even better
than getting them free. I made a typo.

I apologize for my mistake.

Best regards, Richard Harrison, KB5WZI

Incoming radio wave polarisation
 

"Richard Clark" wrote in message
...
On Mon, 17 Mar 2008 09:17:01 -0700, Jim Lux
wrote:

run through a variable combiner

Hi Jim,

As Richard pointed out, a goniometer (what, a 100 years old already?)
works fine for this. I bought one at a Ham swap when I was a
teenager. I also pointed this goniometer/antenna application out to
Arthur to demonstrate what he thought was novel was quite old (in
reference to the work of Tosi and Bellini). Arthur does not
acknowledge prior inventors, so this topic consistently re-emerges
with a fair periodicity. It should reappear around July again.

For those who want to see a schematic of the goniometer and antenna
application, here is a perfectly good example:
http://www.elektronikschule.de/~krau...ng%20-%205.htm

73's
Richard Clark, KB7QHC

Hi Richard

Is it possible that Sheldon Remington is trying to acknowledge Art's
previous work as indicated by his naming him in the title of his article?

J

Incoming radio wave polarisation
 

On Mar 17, 5:29 pm, "Richard Fry" wrote:
Examination of the radiation patterns of horizontal antennas confirms
that they invariably have zero response at zero elevation on their best
azimuths.

_____________

If this were true then most television broadcast stations would have nearly
zero field strength near the earth over much of their present coverage
areas.

Instead, the fields there are directly related to the peak ERP of the TV
station -- which typically is radiated in, or a few tenths of a degree below
the horizontal plane.

RF

So you are saying that Termqn's book has errors?
Amazing!

Incoming radio wave polarisation
 

On Mar 17, 3:28 pm, (Richard Harrison)
wrote:


"----a loop antenna responds much less to the electric induction field
than does a simple wire antenna of comparable intercept area. This is of
importance because electric induction fields predominate in the man-made
noise that causes disturbances in radio receivers, and this explains in
part the popularity of loop antennas in broadcast receivers."

Best regards, Richard Harrison, KB5WZI

I'll have to ponder his statement, but my reg flag is waving...
This almost seems akin to the shielded loop controversy.
It may well be true in whatever manner he is considering, but
for some reason it doesn't seem quite right to me.
Maybe I'm missing something, so I'll await further comments.
MK

Incoming radio wave polarisation
 

On Mon, 17 Mar 2008 23:19:43 GMT, "Jerry"
wrote:

Is it possible that Sheldon Remington is trying to acknowledge Art's
previous work as indicated by his naming him in the title of his article?

Hi Jerry,

Well.....

It does in many ways suggest prior Art is responsible, yes.

73's
Richard Clark, KB7QHC

Incoming radio wave polarisation
 

"Art Unwin" wrote:
If this were true then most television broadcast stations would have
nearly
zero field strength near the earth over much of their present coverage
areas.

Instead, the fields there are directly related to the peak ERP of the TV
station -- which typically is radiated in, or a few tenths of a degree
below
the horizontal plane.

RF

So you are saying that Termqn's book has errors?
Amazing!
______________

art,

Your post above shows that you don't understand this subject, and
what Terman wrote about it. Not so sure about "Termqn," though.

Doesn't your common sense and life experience support
what I stated in my post? If not, why not?

Please consider using "due diligence" and proofreading before
you click your send button. Such will serve you better.

RF

Incoming radio wave polarisation
 

Richard Harrison wrote:
. . .
From researching susceptibility of antennas to noise I came across a
statement interesting to me in Terman`s 1955 opus on page 929:

"----a loop antenna responds much less to the electric induction field
than does a simple wire antenna of comparable intercept area. This is of
importance because electric induction fields predominate in the man-made
noise that causes disturbances in radio receivers, and this explains in
part the popularity of loop antennas in broadcast receivers."

Like so many bons mots lifted from Terman, we have to use a bit of care
in extending it to everyday amateur applications.

A very small loop responds less strongly to the electric field than a
very small dipole only within a fraction of a wavelength of the antenna.
Beyond that, it actually responds more strongly to the electric field
than the dipole does. So at HF, for example, it would be helpful only in
rejecting electric field noise being radiated within a few feet of the
antenna.

Roy Lewallen, W7EL

Incoming radio wave polarisation
 

Roy Lewallen wrote in
:

A very small loop responds less strongly to the electric field than a
very small dipole only within a fraction of a wavelength of the
antenna.

I have seen this expressed as a sensitivity to E and H that imply an
impedance that varies with distance from the antenna, and that it
"bounces around" (that is a technical term, you know) eventually
converging on 120*pi.

Is that correct?

Beyond that, it actually responds more strongly to the electric field
than the dipole does. So at HF, for example, it would be helpful only
in

Roy, accepting that the response of the loop and dipole to electric and
magnetic fields are different close the the antenna, do they not
eventually converge on sensitivity to E and H in the ratio of 120*pi
when immersed in the far radiation field?

I don't know if I have put that sensibly.

My understanding was that when placed a very long way from the sources,
neither one had any advantage in response to the desired signal just by
virtue of their type (loop vs dipole).

Owen

Incoming radio wave polarisation
 

Owen Duffy wrote:
Roy Lewallen wrote in
:

A very small loop responds less strongly to the electric field than a
very small dipole only within a fraction of a wavelength of the
antenna.

I have seen this expressed as a sensitivity to E and H that imply an
impedance that varies with distance from the antenna, and that it
"bounces around" (that is a technical term, you know) eventually
converging on 120*pi.

Is that correct?

They do converge, but only after one change in slope. More below.

Beyond that, it actually responds more strongly to the electric field
than the dipole does. So at HF, for example, it would be helpful only
in

Roy, accepting that the response of the loop and dipole to electric and
magnetic fields are different close the the antenna, do they not
eventually converge on sensitivity to E and H in the ratio of 120*pi
when immersed in the far radiation field?

Yes.

I don't know if I have put that sensibly.

My understanding was that when placed a very long way from the sources,
neither one had any advantage in response to the desired signal just by
virtue of their type (loop vs dipole).

That's correct.

E/H is the impedance of the field and, close to a small loop, the
impedance is small as expected. (As a receiving antenna, this means that
it's relatively more sensitive to the H field than the E field if the
source is very close.) However, the impedance rises rapidly as you get
farther from the loop, and at a fraction of a wavelength, it actually
overshoots 276 ohms. Then, after reaching its peak, it monotonically
approaches 276 ohms from the high side as you get farther and farther
away. A short dipole acts just the same, but with E and H reversed: the
impedance is high very close to the antenna, then overshoots on the low
side, and from there approaches 276 ohms at a great distance. So at all
points except very close, the impedance of the loop's field is actually
higher than that of the dipole's. In practice, the difference is
negligible except perhaps for a very small region, so they behave
virtually the same for signals coming from any distance of, say, a
wavelength or further away.

You can very easily see this behavior with NEC-2 or EZNEC modeling,
using the near field analysis. The free demo version of EZNEC is adequate.

Roy Lewallen, W7EL

Incoming radio wave polarisation
 

Roy Lewallen wrote in
:

.....
actually overshoots 276 ohms. Then, after reaching its peak, it
monotonically approaches 276 ohms from the high side as you get

120*pi or 377?

Owen