Are we having fun yet Joe?


Jul 07 08:41 04, Joe Nicholson wrote to Paul Westell:

 JN>  I wish I still had my waveguide notes and textbooks from the
 JN>  Navy.  But I do remember how the dimensions of waveguides'
 JN>  walls and the dish affected the signal, very much like the
 JN>  construction of RG transmission lines and antenna for
 JN>  radio/TV transmitters.

 JN>  It's possible to lose power out (ERP) with signals reflected
 JN>  back to the transmitter feeding a waveguide, just like those
 JN>  standing waves on a transmission like reflecting back to a
 JN>  radio/TV transmitter.

is this a waveguide feeding a parabolic? i noticed one that had quite a
convoluted shape, and i've since thought about how one would calculate such
a thing, and decided that it makes my head hurt, although it seems that in
principal it should be similar to acoustics though.

i take it that you are recomending that i don't place a waveguide dead
centre at the focus of the parabolic, especially if the parabolic has some
sort of harmonic relationship to the transmission frequency ?

i was thinking that perhaps i might try a piece of tin bent in a simple
curve, rather than try to construct the compound curve of a dish. it is
very simple to draw the curve to start with, but as to the height of the
reflector, i was thinking of making it equal the wavelength. 

if i use a simple 1/4 wave drive element instead of a waveguide, should the
parabolic focus have, or avoid a particular relationship to the frequency? 


hows the weather down there? hot and sunny here.


It could be worse ...
Paul

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