In message
, Art
Unwin writes
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?

Diffraction off the edge of the reflector. It causes backlobes. It's
not a fault.

Brian GM4DIJ
--
Brian Howie

Brian Howie wrote:
In message
, Art
Unwin writes
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?

Diffraction off the edge of the reflector. It causes backlobes. It's
not a fault.

Brian GM4DIJ

Ask him the working frequency and dimensions of his "dish reflector".

Don't be drinking anything when you read his answer.


--
Jim Pennino

Remove .spam.sux to reply.

On Fri, 10 Apr 2009 07:54:41 +0100, Brian Howie
wrote:

Diffraction off the edge of the reflector. It causes backlobes. It's
not a fault.

Hi Brian,

You have hit the nail on the head. More, you have pushed in the tack
with a 10# sledge. This design we are talking about suffers immensely
from the violation of observing what you comment upon.

It is very much a fault.

73's
Richard Clark, KB7QHC