[Moon] septum feed question

[ok1dfc]

Hi Peter, Hi all,
K-parameter from my calculation spread sheet is not critical parameter. When
I was upgrading and working with existing feed developed by Jarda OK1AHH and
used Franta OK1CA, I had many differences. First was, that nobody before me
tested feed like I have designed. K-parameter I have choice as a whole
lambda length. With any flare can be used without, but with the lambda long
square wave guide I have reached better isolation between RX and TX port and
better circularity. I did not find any other solution. Now I have designed
conversion between square and circular wave guide and will have samples soon
for testing. I am expecting that circular wave guide will be only lambda/2
enough, but need more time to test. Conversion part between square and
circular I have calculate to lambda/4. I will keep to inform you all after
test.
Regards

Zdenek OK1DFC
10m dish/QRO EME
144 - 1296 MHz
WAC 432 - 1296 MHz
www.ok1dfc.com
  -----Original Message-----
  From: moon-bounces at moonbounce.info [mailto:moon-bounces at moonbounce.info]On
Behalf Of peter blair
  Sent: Wednesday, May 02, 2007 11:58 AM
  To: moonbounceboard; freetalk moonnet; w1ghz at arrl.net; Rastislav Galuscak
  Subject: [Moon] septum feed question


   Referring to Zdenek's ( OK1DFC) septum calculation file  which  you will
find at http://www.ok1dfc.com/eme/technic/septum/calc.xls  can anyone tell
me what is the significance or importance of the dimension K, the distance
from the end of the last tooth of the septum to the open end of the guide.
    Im not questioning Zdeneks excellent work but I cant understand  why
this should be a specified or critical  parameter.
  If it is a critical parameter in the original ( square ) design is it also
critical in a circular guide?
    Im asking the question widely because I guess by now quite a few people
will have built these  and there should be some experience out there Thanks,
73 Peter G3LTF


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