"Art Unwin" wrote in message
...
On Feb 10, 1:57 am, "Jerry" wrote:
"Harry H" wrote in message

...





The Lindenblad has an overhead null that you might find anoying for
some
high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I sure am
open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design concept.
It is my claim that a DCA is extreemely forgiving of construction
errors
and uses 4 wire dipoles and 50 ohm coax with 5 RFI type ferrites as
"baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would you
have a copy of the article?

HH

Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two pairs
of crossed dipoles. Each pair is spaced 1/4 wave apart and fed in phase.
One pair is physically mounted 90 degrees from the other pair. All four
dipoles are tilted 30 degtrees from vertical. One pair is fed 90 degrees
later than the other pair.
The concept is so simple and straightfoeward that it is probable that the
concept has been developed before I thought of it. But, I have been unable
to find anything published related to this simple "Double Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept and
he found it to be exactly what he needed for reception of NOAA weather
satellite signals. Patrik publishes alot of what I send him related to the
antenna. Patrik shows a section of his web page to describe the DCA to
anyone interested. You can find the QST article in the section Patrik
identifies as ANTENNAS on the first page of his
sitehttp://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to E-mail me,
anytime. Or, if you have any facts or data to show where I am wrong about
how well this antenna performs, or know of something that performs better,
please set me straight.

Jerry KD6JDJ

Looked at the URL
What this antenna is doing is to aproach equilibrium by taking into
account the "weak force" which demands a tilting away from parallelism
or the verticle position away from the surface of the earth, without
which the radiation pattern will not be balanced.
When a U.S.naval base tipped all its verticle antennas at an angle
referenced to earth this prior null must have been of great
inconvenience with respect to defense alertness.

- - - -

A simpler explanation is that the tilt is there to provide a
horizontally-polarised component in the radiated field around the antenna,
as well as a vertically-polarised component, in order to achieve circular
polarisation. The angle of tilt is a design parameter which, along with the
radius of the centres of the dipoles and, in this case, the choice of how
they are phased, collectively determine the axial ratio. The radiation
patterns and match of such an antenna are not affected by its orientation
with respect to the surface of the earth!

Chris