[Moon-net] Fw: Feed choice

[Edward R. Cole]

My appologizes for my speculations on the question posed by Dom.  I await
reading the article written for DUBUS 1/2007.  I am very interested because
I am planning to build this feed at 23cm for my 4.9m dish to be bulit this
summer.  I did build a square OK1DFC model for experimentation but want to
take advantage of the new findings regarding the so-called super-VE4MA feed.

73's Ed - KL7UW

At 02:53 AM 2/8/2007 -0800, Rastislav Galuscak wrote:
>
>Gentlemen,
>
>  The Gain of a dish antenna is given by formula
>
>   
>                                                    π² D²
>                                         G =  ­­­­­­   η
(ratio)                             
>                                                      λ²
>   
>    where D is dish diameter, λ is wavelength, and η is total
efficiency.
>  Efficiency consists of many  individual components  consequently, total
efficiency is a function of their product.  For circular polarization (CP)
the total efficiency, η differ from that of efficiency components for
linear polarization. That is the reason why waveguide which is used as a
feed for linear polarization antennas may have differ size than waveduide
for CP. More  you can find in my and Mr. Hazdra article in 1/2007 DUBUS
magazine.
>Form of electromagnetic field on the septum is very complicated. Some
works about this subject were published in IEEE materials. Using modern
software allows us to optimalize septum dimension. The most suitable
software to do that, appears MICIAN MICROWAVE WIZARD soft. see
www.mician.com Anyway, septum optimalization is not easy  job. You must be
prepared to spend lot of time with calculations.
>   
>        Sincerely,
>                         Rasto, OM6AA
>
>
>
>   
>  
>
>DEHAYS Dominique <dominique.dehays at enac.fr> wrote: Hi all ,
>
>if my informations are acurate ,  there will be a "SUPER VE4MA" feed with 
>Septum polarizer described in DUBUS for 23 and 13cm  ( maybe in the next 
>issue? ). So you will get good information.
>I had the opportunity to read it in avance ( tnx to the author). I just 
>wonder one thing : there is some calculations done in the article , one of 
>them is feed horn diameter. I saw that this diameter is different for 
>linear and for circular polarisation , I wonder why? Anybody knows?
>
>73's Dom/F6DRO/JN03TJ 
>
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