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Re: Quadrifilar home brew


>if you research a little bit in several articles published in
>non-ham magazines and have a look at commercial use of LEO
>satellites in the UHF band the circular polarised antenna of
>choice in most commercial applications is in fact the quadrifilar
>helix antenna (QFH). It offers excellent circularity over a very
>wide hemispherical range and offers a good performance/size ratio
>apart from being an omnidirectional antenna.


Hi Oscar,

Thank you for that wealth of information.  I certainly look forward to the 
results of your efforts....It took me about 5 iterations of the "short" QFH 
to get the swr down, and then two more to determine circularity!!  At that 
time there was nothing published to indicate which twist for which polarity...

I attempted many of Kilgaus' designs for the tall version, never could get 
the swr down to a reasonable value.  And there were lobes all over the 
place...In contrast to the "short" version that has a very reasonable 150 
degree beamwidth, albeit at boresite...

I solved that with a light weight rotor mounting a 435 and 2M version at 45 
degrees EL..

A friend in Australia wrote a computer program for me to switch any number 
of fixed AZ/EL antennas using InstantTrack to do the relay switching.  It 
works extremely well with attendant gain I estimate at 3db, in any desired 
direction...Worked ok on AO40 at the prime squint angles...

I guess you can tell I can hardly wait to continue with P3E!!

            73, Dave wb6llo@amsat.org
                    Disagree: I learn....

               Pulling for P3E... 

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