[amsat-bb] Helix phase center

[John Wright <g4dmf@xxxxxxxxx>]

Is there any definitive definition of where the phase center of helix 
should lie? I am currently trying to setup a 60cm offset dish for Mode S, I 
have made a 3.5 turn helix, that has about the right beam-width to feed the 
dish, but would like to have a rough idea as to where the helix should be 
in relation to where the Ku band LNB was. I think that the phase center for 
the LNB is probably inside the mouth of the horn, the feed point is 
probably within the area covered by the original mounting clamp, so its a 
bit difficult deciding where to put the helix. I've tried to find data on 
Ku band LNB's to see if I can find where the phase center is on them, but 
have been unsuccessful. Perhaps it's not really that critical? Any help 
appreciated.
John

____________________________

      G4DMF  QTHR   IO93HA
      Amsat-UK Member 5372
          g4dmf@amsat.org
      http://www.g4dmf.co.uk
____________________________

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