On Apr 10, 9:50*am, "Dale Parfitt" wrote:
"Art Unwin" wrote in message

...

I made a helical end fed antenna that is inside a cone shaped
reflector
The reflector is made from 1/2" mesh steel with an aluminum foil liner
and connected to the braid of the feed coax. No baluns are used, just
direct connections.
I was surprised to hear signals from the rear!
I thought that a dish reflector prevented such signals getting to the
receiver. So what can be wrong with the reflector or can signals get
reflected back from the frontal area? Antenna is at a 40 foot height
Any ideas as to what the fault could be?
Regards
Art
I have no experience with dishes thus the question Note, the helical
antenna does not protrude beyond the dish envelope.
Art

There is a lot of very important information missing here.
What frequency are we talking about and what is the dish diameter?
Do you have any idea as to what your edge taper is or sidelobes?

Dale W4OP

Dale
I thought that if the radiator was in the reflector envelope, that is
the radiator is below the top of the cone then there should be no
radiation from the rear though possibly a little edge refraction. I
know little regarding dish reflectors thus the question. I am of the
opinion that radio is a matter of particles and not waves so I can
easily visualize impregnation of the shield at the center as per
Rutherford foil and particle experiments, but I am not ready to jump
because of edge taper and other things that I am not aware of
What is very clear from dish radiation patterns in the books that
there is a localised radiation congregation at the dish axis rear
which appears unexplainable.
at the rear at the dishes axis tho it is in the area of direct impact
I appreciate the comments and thoughts applied but not the nonsensicle
writings of Richard who is wired so differently from the rest of us.
These signals appear at all frequencies though I fail to see what the
impact of frequency is because of the reflector envelope or umbrella.