On Apr 10, 8:45*pm, Tom Ring wrote:
Art Unwin wrote:

The posting is about dishes not antennas. I have not read about a dish
that does not emit signals to the rear. Now I have built one and find
to my surprize that it does accept signals from the rear ! All very
simple, the radiator is resting at the bottom of a cone and the top of
the radiator does not stick out beyond the reflector. Since you do not

Well, to start with Art, a cone reflector doesn't meet the definition of
a dish antenna.

I'm sorry, but they just aren't the same thing.

I surprizzzed you missed the difference.

tom
K0TAR

Tom
I asked the question as I am not personly knowledgable about dish
style reflectors.
I do read a lot and I read a paper once where it was found that a cone
shaped reflector produced increased gain when used with a helix
antenna, so I made one to try it out. Personaly I see it more as a
horn and not as a dish with a radiator at a phase control difference
from the reflector? Either way I do not understand how that I can hear
signals to the rear if the reflector envelope encloses the radiator
thus the question. Note that a helix radiates differently from the
normal dish radiator such that phasing does not enter the design which
is why you see planar dishes or "cups".
Thus questions with respect to reflector diameter are not
pertinentwhen the radiator is enclosed.