"Matt" wrote in message
...
I used gutter pipe (3 by 5 or so) in one band and built one out of
brass
@
2.5 Ghz worked like a champ.
Slots were 1/4 wave (freespace) and seperated by 1/2 wave (speed of
waveguide, not freespace)

How do you figure the speed in waveguide rather then free space?


It is in several books, called lambda sub-g
you could probably google it, starting with waveguide transmission.
I can't remember, but I think is is about 75 to 85%
It is determined by the dimentions of the waveguide, (same with coax, and
material slows it down further)
lambda is wavelength in free space.



Matt


Feed was 1/4 wave sticking into the rect pipe, in the middle.
Round pipe should work just fine.