wrote in message
...
On Aug 10, 8:23 am, Art Unwin wrote:


What stands out for me is the audio improvement.

Only very high Q antennas should noticeably effect audio.
Comparing a dipole to say a turnstile, you should notice
no real difference at all.

I have though that also, but I have noticed that on 75 meters there
sometimes seems to be a differance in the voice of the other station when I
switch from my off center fed antenna at 50 feet and a dipole at 20 feet.
This is when signals are around the same on either antanna. Around the s-9
point. I am using an Icom 746pro and an external switch to change the
antennas.

I also did some experiments in the early '70s to see if CP would reduce
fading. I built a couple of types of omnidirectional CP antennas -- a
"skew planar", and a copy of a commercial FM BC antenna, for mobile use
with the local 450 MHz repeater. I soon discovered that as soon as I
placed the antenna over the top of the car, the polarization became
nearly linear. I've since learned that it's because of the nature of the
reflections from the ground plane, and it's easily seen with EZNEC+.
When I put the antenna far enough away from the car to minimize
reflections, the lowered gain offset any possible advantage. Overall,
they worked out worse than a conventional vertically polarized antenna.
It might have been interesting to try CP at the repeater, but that was
never done.

The problem with ground reflection ruining the circularity makes it very
difficult to achieve circular polarization for HF skip communication. A
second problem is that the majority of CP antennas, such as the
quadrature fed crossed dipole "turnstile", are circular only directly
broadside, and increasingly elliptical as you move away from that direction.

Roy Lewallen, W7EL

Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Is there a CPOL advantage for atmospherically propagated HF? I can
think of some disadvantages.

On Aug 10, 5:21*pm, dave wrote:
Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Is there a CPOL advantage for atmospherically propagated HF? *I can
think of some disadvantages.

I am all ears. Go for it

Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Please provide examples of commercial antennas that are CP. Space
communication antennas are not ok to include.

Please give counts of CP versus linear in commercial use.

tom
K0TAR

On Aug 10, 11:14*pm, tom wrote:
Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Please provide examples of commercial antennas that are CP. *Space
communication antennas are not ok to include.

Please give counts of CP versus linear in commercial use.

tom
K0TAR

Use your own thread to ask for assistance on your question.
Be prepared to answer why you are requesting this personal service .
I asked a question on this thread with respect to the main advantage
for hams that linear
polarization has over CP. I have no resistance to change if it can be
justified. I see
that it can pick up signals that linear antennas cannot hear because
of a 30 db attenuation
where as CP has only a 3 db attenuation!
So what is it on the other side of the coin is what this thread is
posing to those who are familiar with respect to radiators.

"Art Unwin" wrote in message
...
On Aug 10, 11:14 pm, tom wrote:
Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Please provide examples of commercial antennas that are CP. Space
communication antennas are not ok to include.

Please give counts of CP versus linear in commercial use.

tom
K0TAR

Use your own thread to ask for assistance on your question.
Be prepared to answer why you are requesting this personal service .
I asked a question on this thread with respect to the main advantage
for hams that linear
polarization has over CP. I have no resistance to change if it can be
justified. I see
that it can pick up signals that linear antennas cannot hear because
of a 30 db attenuation
where as CP has only a 3 db attenuation!
So what is it on the other side of the coin is what this thread is
posing to those who are familiar with respect to radiators.

Cross polarization can be used to provide isolation for duplex links or
co-channel sharing.

Use your own thread to ask for assistance on your question.
Be prepared to answer why you are requesting this personal service .
I asked a question on this thread with respect to the main advantage
for hams that linear
polarization has over CP. I have no resistance to change if it can be
justified. I see
that it can pick up signals that linear antennas cannot hear because
of a 30 db attenuation
where as CP has only a 3 db attenuation!
So what is it on the other side of the coin is what this thread is
posing to those who are familiar with respect to radiators.

Cross polarization can be used to provide isolation for duplex links or
co-channel sharing.


I think that you are looking at it from the wrong point of view. CP does not
have 3dB attenuation, but a linearly polarized signal received on a CP
antenna will be 3db down (whether that be H, V or slant).

So for amateur use CP is useful in that with another CP station multipath
due to reflections will be reduced (reflections taking on the opposite hand
CP and thus attenuated). However, if a CP antenna is used to receive H or V
you may well not see the full 3dB reduction due to twisting of the
polarization on the path. In fact over some paths the signal on a CP antenna
will be better than on a linearly polarized antenna due the a greater
attenuation due to polarization twisting.

Of course the best of both worlds is to have a crossed yagi with a phase
switching box so that you can select CP (both hands) H, V or slant 45 both
ways.

Commercially (terrestrially) I don't think that CP is used much except
perhaps on microwave point to point links.

Jeff

On Aug 10, 12:24*am, Art Unwin wrote:
The majority of antennas used today are (commercial) circularly
polarized
Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?

Where did you get the info that most commercial antenna use is
circular polarity?

Jimmie

snpOn Aug 11, 10:16*am, "Jeff" wrote:


Of course the best of both worlds is to have a crossed yagi with a phase
switching box so that you can select CP (both hands) H, V or slant 45 both
ways.

Jeff, I want the" best of both" worlds but before one jumps one needs
to know the advantages and disadvantages of both first. To be frank, I
do not know what happens to all signals when they are reflected
including the reflection off the ground to a receiver or a direct hit
on the receiver from our upper layers so I have no way of undertaking
a comparison. Now most hams are resistant to change or will only
follow the majoratory thus the questions "who has the majoratory". For
me I see CP as an ideal approach for smaller volume antennas which is
the "holy grail" for hams, but one has to determine if smaller is
important enough to overide possible faults.Now I have a whip antenna
( no ground plane) on my tower that is CP for top band but the bands
are poor it is difficult to determine its worth especially since
there are no similar radiators out there. So I fall back and ask for
"what is known already" as there is no point in re inventing the
wheel. Is that so bad?
Now before the catwalling about the possibility of having a whip (a 5
foot pole) for top band
my intention is to release all that during the next month. So lets not
waste energy in side tracking comments and stay on the essence of this
thread. Remember the last time I intended to release it was evident
that most did not want to hear it........ so I went along !





Commercially (terrestrially) I don't think that CP is used much except
perhaps on microwave point to point links.

Jeff