art wrote:
On 14 Feb, 11:01, "art" wrote:
On 14 Feb, 09:55, "David G. Nagel" wrote:





art wrote:
On 13 Feb, 22:18, "Jerry Martes" wrote:
"Bobby" wrote in message
ups.com...
All,
How do you determine the axial ratio from a RHCP wave to a LHCP wave
from an antenna? In essence, I need an axial ratio transformation from
RHCP to LHCP.
Any ideas on the equation or where I can find it will be helpful.
Thanks.
Bobby.
Hi Bobby
If you are working with an antenna that radiates RHCP it is totally
insensitive to LHCP.
If you have an antenna that radiates "RHCP" (or LHCP) the axial ratio is
the ratio of the Minor axis to the Major axis of the E field. So, it
varies from zero to one as the radiated field varies from Linear to
Circular.
Jerry
You mentioned insensetivity above, are there any other polarities
insensitive to others ? I note that weather antennas are now migrating
to
dual diversity antennas for horizontal and vertical, is it possible to
totally isolate those too.?
Art
Any cross polarization situation will exhibit insensitivity to others.
For instance take a vertical antenna and a horizontal antenna at a
distance. There is a signifant reduction in signal strength.
Or take a dipole oriented NS and a dipole oriented EW and you will see a
loss of signal also.
Dave WD9BDZ- Hide quoted text -
- Show quoted text -
David, could you add to your posting some of it doesn't seem to jive.
Art- Hide quoted text -

- Show quoted text -

David , maybe it was I that was not so clear.
My arials are based around a cluster of elements that are at various
placement with respect to each other tho all are resonant as is the
cluster as a whole. So when it is used for diversity operation because
more than one element is resonant choices can be made as to where to
feed to advantage
as quick as possible with a change over such that the reflection is
meaningful with respect to time. I don't believe that the weather
people radiate both at the same time as the search is for purity with
respect to polarity. In fact all the arials ive seen cannot possibly
be pure since they all seem to have elements in the vertical position
which cannot lead to purity in any form. I saw one in a antenna book
( shelnikov)where the elements were in helical form one behind the
other at a 90 degree offset but I have no further knoweledge of that
one. Somebody mentioned that some radios are now made with two ports
such that the receive portion automatically switches to the loudest
signal to overcome fading so I may well be incorrect about
simultaneous transmissions or even if two arials are in use.
Art

Art;

I responded to your other email but what you are saying here is that you
are using multiple antenna's which are selected automatically to sense
the strongest signal reguardless of the orientation of the received
signal. i.e. if the signal is at 45 degrees the antenna that is fixed to
a 45 degree angle will be the strongest signal. If I have it correct it
makes perfect sense but is not cross or circular polarization just
rotated wave front.

Dave WD9BDZ