[Moon] Echo vs focal-cm for 1296 MHz - de SM5LE

[M. Watanabe]

Hello Sven, SM5LE

Remarkable difference of dBs is found in your experiment! 

How did you measure the distance from the calculated focal 
point?  
I think your feed (and the feed in general) may have the phase 
center a few centimeters inside the aperture of the feed. 

The distance change on axis may give some more  influence to 
the depth of null; while the maximum gain might drop a litte bit. 

I don't want to be proud of it but the feed of my 4.4m dish is 
located 7 cm far from the ideal position.  Still it works well. 
Hi

What's more is the axial diviation, specially in a deeper dish, 
which deteriorates the antenna gain and beam pattern so rapidly. 


Mike JH1KRC


---- SM5LE <sm5le at telia.com> wrote: 
> Hi
> 
> Just measured echo-dB  vs. focal distance in cm.
> The diagram shows deviation from theoretic.
> 
> See
> SM5LE HomePage at : http://web.telia.com/~u14901544/
> 
> 
> 73 Sven SM5LE
> 
> ps   Yes,  I was some dB out during ARRL contest. Sorry for that !