On Apr 10, 1:07*pm, "Rollie" wrote:
Maybe the coax ground is insufficent and a seperate ground from mother earth
is required.....Maybe

"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

Rollie
I checked.
The coax ground and the reflector is grounded at the same place at the
top of the tower. All horizontal coax is buried. Seems like the dish
reflector does not get a lot of attention from ham operators !
Art

Art Unwin wrote:
On Apr 10, 1:07Â*pm, "Rollie" wrote:
Maybe the coax ground is insufficent and a seperate ground from mother earth
is required.....Maybe

"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

Rollie
I checked.
The coax ground and the reflector is grounded at the same place at the
top of the tower. All horizontal coax is buried. Seems like the dish
reflector does not get a lot of attention from ham operators !
Art

Hmmm, I guess this guy just talks to himself.

http://www.signalone.com/kb2ah/KB2AHantennas.html


--
Jim Pennino

Remove .spam.sux to reply.

On Fri, 10 Apr 2009 19:30:03 GMT, wrote:

Hmmm, I guess this guy just talks to himself.

For himself.

Artifice: I have a novel and mysterious design emploiting Rutherford
partical evasion without baluns and using a gauss reflectionater.

Ham: What is its front to back rejection?

Artifice: I gets signals in all directions! Not just front or back.

Ham: Then why do you say it -um- evades something or other (sigh)?

Artifice: Well, this is not part of the design of not getting the
forward proceeding back signals.

Ham: So, it doesn't work.

Artifice: It works perfectly, just not as well as gaussian
reflectionating mechanics would expect unless these particals are
accelerated to high speeds by the weekend force.

Ham: So, why doesn't my antenna get this kind of signal?

Artifice: Because you read books from the libraries of the hooded
priests who refuse to backnowledge my inventions!

Ham: Why would I want to listen to these signals if I read your
books?

Artifice: Then you could enjoy the Fill-harmonic richness of my
single channel stereoid transmissions.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Fri, 10 Apr 2009 19:30:03 GMT, wrote:

Hmmm, I guess this guy just talks to himself.

For himself.

Artifice: I have a novel and mysterious design emploiting Rutherford
partical evasion without baluns and using a gauss reflectionater.

Ham: What is its front to back rejection?

Artifice: I gets signals in all directions! Not just front or back.

Ham: Then why do you say it -um- evades something or other (sigh)?

Artifice: Well, this is not part of the design of not getting the
forward proceeding back signals.

Ham: So, it doesn't work.

Artifice: It works perfectly, just not as well as gaussian
reflectionating mechanics would expect unless these particals are
accelerated to high speeds by the weekend force.

Ham: So, why doesn't my antenna get this kind of signal?

Artifice: Because you read books from the libraries of the hooded
priests who refuse to backnowledge my inventions!

Ham: Why would I want to listen to these signals if I read your
books?

Artifice: Then you could enjoy the Fill-harmonic richness of my
single channel stereoid transmissions.

73's
Richard Clark, KB7QHC

Sorry Richard, but that's definitely Memorex. Nice try though.

tom
K0TAR

"Art Unwin" wrote in message
...
Seems like the dish
reflector does not get a lot of attention from ham operators !

certainly not by 160m ham operators! welcome back art, needed something to
brighten up a dreary saturday morning!

On Apr 10, 2:14*pm, Art Unwin wrote:
The coax ground and the reflector is grounded at the same place
at the top of the tower. All horizontal coax is buried.
___________

An r-f ground does not exist at the top of your tower,
or any tower.

Unless some means is provided to prevent r-f current flow
on the outside of the coax and on the tower structure,
they will radiate/receive r-f energy.

This probably accounts for most of the pattern effects
that you didn't expect to have (regardless of the real
pattern that your cone and helix generates).

RF

Richard Fry wrote:
Unless some means is provided to prevent r-f current flow
on the outside of the coax and on the tower structure,
they will radiate/receive r-f energy.

Thus making the vertical antenna longer than 5/8WL.
Using the top of the tower for a ground simply
makes the tower part of the antenna system turning
the entire array into an off-center-fed vertical
dipole with the bottom end grounded. For instance,
a 1/4WL 20m monopole mounted on top of a 60 foot
tower using the tower as the coax shield ground
has a take-off-angle of 57 degrees. The highest
RF current is near the middle of the tower. :-(

To make matters even worse: I had a similar problem
with drooping 1/4WL radials DC insulated from the tower.
The drooping radials coupled RF into the tower and
turned it into a radiator which screwed, oops, I
mean skewed the radiation pattern upwards. It took
me a long time to figure out why my horizontal dipole
was magnitudes better than my 1/4WL vertical on top of
the 1.25WL tall tower which was grounded at the bottom
and floating at the top.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On Apr 19, 8:09*am, Cecil Moore wrote:
Richard Fry wrote:
Unless some means is provided to prevent r-f current flow
on the outside of the coax and on the tower structure,
they will radiate/receive r-f energy.

Thus making the vertical antenna longer than 5/8WL.
Using the top of the tower for a ground simply
makes the tower part of the antenna system turning
the entire array into an off-center-fed vertical
dipole with the bottom end grounded. For instance,
a 1/4WL 20m monopole mounted on top of a 60 foot
tower using the tower as the coax shield ground
has a take-off-angle of 57 degrees. The highest
RF current is near the middle of the tower. :-(

To make matters even worse: I had a similar problem
with drooping 1/4WL radials DC insulated from the tower.
The drooping radials coupled RF into the tower and
turned it into a radiator which screwed, oops, I
mean skewed the radiation pattern upwards. It took
me a long time to figure out why my horizontal dipole
was magnitudes better than my 1/4WL vertical on top of
the 1.25WL tall tower which was grounded at the bottom
and floating at the top.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Thank you all for those points raised. I added the ground to the dish
because I was getting a lot of static one night, I have not had any
since but
I need time to compare. The grounding line is a heavy silver coated
braid connected
to each section and to ground. My coax drops to ground and then goes
underground
for a 100 feet or so and grounded again when it resurfaces.
Regards
Art

Art Unwin wrote:
Thank you all for those points raised.

Moral is: There's no such thing as earth "ground"
at 50 feet in the air. There are only ground planes,
counterpoises, and other conductors that become part
of the antenna system. Even the ground wire on an
artificial ground device radiates.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On Apr 19, 9:13*am, Cecil Moore wrote:
Art Unwin wrote:
Thank you all for those points raised.

Moral is: There's no such thing as earth "ground"
at 50 feet in the air. There are only ground planes,
counterpoises, and other conductors that become part
of the antenna system. Even the ground wire on an
artificial ground device radiates.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

What if one put a diode in that ground line?