On Feb 16, 10:03*am, JosephKK wrote:
On Tue, 10 Feb 2009 18:12:26 -0000, "christofire"



wrote:

"Jerry" wrote in message
...

"christofire" wrote in message
.. .
"Jerry" wrote in message
. ..

"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 site
http://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

... but surely this is the same as a Lindenblad array? *The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris

*Hi Chris

*Several, well educated, antenna experts insist that the DCA is actually a
Lindenblad. * If you thought the DCA is a Lindenblad, you are not alone.
*The DCA is not a Lindenblad. * The array of four dipoles in a Lindenblad
are fed to produce an overhead null. * The four dipoles in a DCA are fed
to produce no overhead null. * The DCA is a hemispheric coverage CP
antenna. The Lindenblad is not.
*Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. * I knew nothing about Lindenblad until after recognizing the
DCA concept.

* * * * * * * * * * * Jerry m * *KD6JDJ

* * * * * * * * * * *Jerry

Perhaps it's a rather fine distinction to say an antenna that has the same
physical form as the Lindenblad array is something different because the
elements are driven differently. *The original version that he patented
didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...ry_UWB_antenna...)
but it was the configuration of four slanted dipoles around a central pole
that appears to have borne his name since 1941. *Henry Jasik's 'Antenna
Engineering Handbook' (now by John L. Volakis, Richard C. Johnson and Henry
Jasik, Chapter 29, Page 34) refers to the configuration as a Lindenblad
array, without being specific about the way the dipoles are driven.
However, applying new names to antennas that exploit well known
configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be some
value in mentioning that it is a development of the Lindenblad array - you'd
certainly need to demonstrate awareness of, and distinction from, the prior
art if you were to seek a patent.

Chris

Interesting article, it describes the Lindenblat array as a quartet of
coaxial horns. *Not the same as a quartet of dipoles at all.

Actually, it's not much different.. Both are radiators that radiate a
linearly polarized signal. The Lindenblad (and variants) make the CP
with two dipoles canted relative to each other and fed with a phase
shift (same idea as crossed yagis for Satellite CP antennas). The "two
dipole" thing radiates in both directions, of course. Add another pair
pointing at 90 degrees from the first, and you get roughly
omnidirectional coverage. You can do the same thing with 4 (or 3 or
27) CP horns arranged in a circle.

Most of the fooling around with dimensions and spacing and phasing has
to do with the overall pattern and just how circular it is at which
look angles.