receive polarity
 

Has there ever been a study that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

receive polarity
 

On Sun, 14 Feb 2010 20:51:21 -0800 (PST), Art Unwin
wrote:

Has there ever been a study that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

Yes. I did one for a company doing exactly that at various
frequencies between 120 to 450Mhz. Sorry, but I don't have a copy of
the report. For convenience, we use ham frequencies for most of the
testing. What we found is that once a signal is reflected, the
reflected signals polarization is fairly random. There are few flat
plate reflectors in both man made and natural objects. The measured
result was a mess of varying polarization angles.

You can expect similar results for HF signals reflected off the
ionosphere with the added complexity of Faraday rotation.

However, it is beneficial to build polarization insensitive antennas.
In a common dipole, there's very little loss for polarization mismatch
until you get very close to perpendicular. There, the signal drops
off quickly. Filling in this hole is considered to be a good thing.

You can get a crude idea of how it works using an Adcock DF antenna
array, or just two cross polarized dipoles. Since you're not building
a direction finder, the crossed dipoles are easier to explain. Just
setup two perpendicular dipoles with the center feeds fairly close
together. Connect two well matched receivers to the two antennas.
Connect the IF or audio outputs to the vertical and horizontal of an
oscilloscope. The resulting Lissajous pattern will give you a rough
idea of the polarization (assuming the signal arrives from above).
Pick a strong steady signal like WWV. You'll probably see the
polarization change erratically when the skip is in. (Last time I did
this was 20 years ago). You'll also see that vertical and horizontal
parts of the Lissajous display to wander around in amplitude fairly
independently. This is the main advantage of a polarization
independent antenna. The antenna will automagically select the
strongest polarization to feed the receiver.

There are circularly polarized HF antennas, but I'm too lazy to Google
for them tonite.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

receive polarity
 

On Feb 14, 11:26*pm, Jeff Liebermann wrote:
On Sun, 14 Feb 2010 20:51:21 -0800 (PST), Art Unwin

wrote:
Has there ever been a study *that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

Yes. *I did one for a company doing exactly that at various
frequencies between 120 to 450Mhz. *Sorry, but I don't have a copy of
the report. *For convenience, we use ham frequencies for most of the
testing. *What we found is that once a signal is reflected, the
reflected signals polarization is fairly random. *There are few flat
plate reflectors in both man made and natural objects. *The measured
result was a mess of varying polarization angles.

You can expect similar results for HF signals reflected off the
ionosphere with the added complexity of Faraday rotation.

However, it is beneficial to build polarization insensitive antennas.
In a common dipole, there's very little loss for polarization mismatch
until you get very close to perpendicular. *There, the signal drops
off quickly. *Filling in this hole is considered to be a good thing.

You can get a crude idea of how it works using an Adcock DF antenna
array, or just two cross polarized dipoles. *Since you're not building
a direction finder, the crossed dipoles are easier to explain. *Just
setup two perpendicular dipoles with the center feeds fairly close
together. *Connect two well matched receivers to the two antennas.
Connect the IF or audio outputs to the vertical and horizontal of an
oscilloscope. *The resulting Lissajous pattern will give you a rough
idea of the polarization (assuming the signal arrives from above).
Pick a strong steady signal like WWV. *You'll probably see the
polarization change erratically when the skip is in. *(Last time I did
this was 20 years ago). *You'll also see that vertical and horizontal
parts of the Lissajous display to wander around in amplitude fairly
independently. *This is the main advantage of a polarization
independent antenna. *The antenna will automagically select the
strongest polarization to feed the receiver.

There are circularly polarized HF antennas, but I'm too lazy to Google
for them tonite.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Thank you for that!
I have not seen the like printed any where soto me it is good stuff.
When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains. I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

receive polarity
 

On Feb 15, 11:01*am, Art Unwin wrote:
On Feb 14, 11:26*pm, Jeff Liebermann wrote:



On Sun, 14 Feb 2010 20:51:21 -0800 (PST), Art Unwin

wrote:
Has there ever been a study *that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

Yes. *I did one for a company doing exactly that at various
frequencies between 120 to 450Mhz. *Sorry, but I don't have a copy of
the report. *For convenience, we use ham frequencies for most of the
testing. *What we found is that once a signal is reflected, the
reflected signals polarization is fairly random. *There are few flat
plate reflectors in both man made and natural objects. *The measured
result was a mess of varying polarization angles.

You can expect similar results for HF signals reflected off the
ionosphere with the added complexity of Faraday rotation.

However, it is beneficial to build polarization insensitive antennas.
In a common dipole, there's very little loss for polarization mismatch
until you get very close to perpendicular. *There, the signal drops
off quickly. *Filling in this hole is considered to be a good thing.

You can get a crude idea of how it works using an Adcock DF antenna
array, or just two cross polarized dipoles. *Since you're not building
a direction finder, the crossed dipoles are easier to explain. *Just
setup two perpendicular dipoles with the center feeds fairly close
together. *Connect two well matched receivers to the two antennas.
Connect the IF or audio outputs to the vertical and horizontal of an
oscilloscope. *The resulting Lissajous pattern will give you a rough
idea of the polarization (assuming the signal arrives from above).
Pick a strong steady signal like WWV. *You'll probably see the
polarization change erratically when the skip is in. *(Last time I did
this was 20 years ago). *You'll also see that vertical and horizontal
parts of the Lissajous display to wander around in amplitude fairly
independently. *This is the main advantage of a polarization
independent antenna. *The antenna will automagically select the
strongest polarization to feed the receiver.

There are circularly polarized HF antennas, but I'm too lazy to Google
for them tonite.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Thank you for that!
I have not seen the like printed any where soto me *it is good stuff.
When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains. I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

What is/are "polarizations gains". That's a term with which I am not
familiar.

Jimmie

receive polarity
 

On Feb 15, 4:51*am, Art Unwin wrote:
Has there ever been a study *that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

there have been studies of polarization of signals over various paths
and frequencies. but i don't know that anyone has studied their
polarity... why don't you try that and let us know how it comes out.

receive polarity
 

On Mon, 15 Feb 2010 14:07:35 -0800 (PST), JIMMIE
wrote:

On Feb 15, 11:01*am, Art Unwin wrote:
I have not seen the like printed any where soto me *it is good stuff.
When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains. I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

What is/are "polarizations gains". That's a term with which I am not
familiar.

Jimmie

It's part of Polarity Therapy:
http://en.wikipedia.org/wiki/Polarity_therapy
I think it has something to do with yin and yang polarization.
Applying acupuncture to the coax cable is known to activate and
improve the flow of Chi, as well as increase the life force energy,
which is what produces the necessary gain.

(Sorry, I couldn't resist).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

receive polarity
 

On Mon, 15 Feb 2010 14:07:35 -0800 (PST), JIMMIE
wrote:

What is/are "polarizations gains". That's a term with which I am not
familiar.

Hi Jimmie,

EZNEC, for one, reports antenna "gain"/directivity (re dBi) for each
polarization, azimuthum or elevation; or their sum as a total field
for a 3D model.

When two antennas (one receive, one transmit) are cross polarized, the
gain between them can vanish to zero. In a real application this zero
is something larger, but still small like 30dB down compared to two
antennas employing the same polarization.

This last is observed in line of sight transmissions of VHF and above
(try hitting your favorite 2M repeater with the wrong antenna
polarization orientation). It is not so common at HF as long paths
(aka skip) can blur the polarization (as can nearby reflectors for any
frequency) causing intermittant fading.

73's
Richard Clark, KB7QHC

receive polarity
 

On Feb 15, 4:43*pm, Dave wrote:
On Feb 15, 4:51*am, Art Unwin wrote:

Has there ever been a study *that shows the relative consistency of
received signal polarity to see if it would be advantageous for multi
polarity receive antennas?

there have been studies of polarization of signals over various paths
and frequencies. *but i don't know that anyone has studied their
polarity... why don't you try that and let us know how it comes out.
___________

Apparently Art believes that a radiated, linearly-polarized a-c
waveform has a unique polarity, rather than a unique polarization.

RF

receive polarity
 

On Mon, 15 Feb 2010 08:01:18 -0800 (PST), Art Unwin
wrote:

I have not seen the like printed any where soto me it is good stuff.

This might offer a clue as to how such antennas are built:
http://ieeexplore.ieee.org/iel3/4812/13333/00608613.pdf?arnumber=608613
http://www.springerlink.com/content/g215405815642611/
Plenty more under IEEE Ants and Props search. Check if your local
library or college library has a subscription:
http://www.ieeeaps.org
http://ieeeaps.org/aps_trans/

When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains.

If you use a circularly polarized antenna, and feed it a linearly
polarized signal (either vertical or horizontal) you'll see a -3dB
polarization mismatch loss.
http://www.antenna-theory.com/basics/antennapol.php

I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

Nope. According to my friends that do contesting, the major
requirement of an antenna is NOT to maximize the gain in all
directions. It's to reduce the gain to the side and back, where all
the other interfering stations are usually located. Directionality is
important or all you're going to hear are other local hams. A truely
isotropic antenna is fairly useless for contesting. (Note: I don't
do contesting).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

receive polarity
 

On Feb 15, 6:02*pm, Jeff Liebermann wrote:
On Mon, 15 Feb 2010 08:01:18 -0800 (PST), Art Unwin

wrote:
I have not seen the like printed any where soto me *it is good stuff.

This might offer a clue as to how such antennas are built:
http://ieeexplore.ieee.org/iel3/4812/13333/00608613.pdf?arnumber=608613
http://www.springerlink.com/content/g215405815642611/
Plenty more under IEEE Ants and Props search. *Check if your local
library or college library has a subscription:
http://www.ieeeaps.org
http://ieeeaps.org/aps_trans/

When I model a polarization independent antenna the individual gains
confuse me as each of the individual gains are some what 3 db down
from the "total" gain. In other words "total" is not the addition of
all the polarizations gains.

If you use a circularly polarized antenna, and feed it a linearly
polarized signal (either vertical or horizontal) you'll see a -3dB
polarization mismatch loss.
http://www.antenna-theory.com/basics/antennapol.php

I find it very difficult to get my mind
wrapped around that fact. On the surface it would suggest that
competition types would benefit from a polarization independent
antenna.

Nope. *According to my friends that do contesting, the major
requirement of an antenna is NOT to maximize the gain in all
directions. *It's to reduce the gain to the side and back, where all
the other interfering stations are usually located. *Directionality is
important or all you're going to hear are other local hams. *A truely
isotropic antenna is fairly useless for contesting. *(Note: *I don't
do contesting).

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

To be honest Jeff the antennas I design are based on starting with a
full wavelength radiators which I presume you are already aware of.
Initially I was basing efficiency on all forces being accounted for
with a higher gain resulting. In fact this aproach to design provides
diversity of polarizations instead of linear thus linear seamed to
supply top gains.
The full wave length aproach gives the option of dual polarity or even
all forms.
The penalty is usually in the 1db range where as the multiple polarity
may drop down a bit on gain but makes use of signals that a linear
design cannot hear as well as zero side lobes and good front to rear
figures. So without knowing what polarizations one has to deal with a
reasonable choice is hard to come by. On top of these questions one
has to look t what "gain" really represents since cross polarization
can be reduced to just noise with the rest of the db gain value
representing quality signal. Thus it is difficult to quantify gain
when the real advantage comes about on weak signals that others
cannot hear. In other words gain itself is not important unless it is
a measure of discernabilitity or quality above
noise or none matching polarities.
Two antenna designs come to mind 1 is the two element array that can
supply 2 polarities,
horizontal and one direction circular and 2 the helical that can
accept all that is thrown at it
with a prime gain around 13 db and 10 db for the others. Thus if
polarizations are random
with weather fluctuations in city or wooded area it would seam
reasonable to discard linear forms in favour of helicals. To sum up,
all the above has placed me on a zero level as to what antenna
efficiency really means which to the reader must now be obvious, as
one does not know what variables should be weighted and by how much.,