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


The last time he talked about it, it was "designed" to operate on the
160 meter band and the "reflector" was 3 meters in diameter.

No, those numbers are not typos.


--
Jim Pennino

Remove .spam.sux to reply.

On Apr 10, 10:15*am, wrote:
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

The last time he talked about it, it was "designed" to operate on the
160 meter band and the "reflector" was 3 meters in diameter.

No, those numbers are not typos.

--
Jim Pennino

Remove .spam.sux to reply.

That antenna was when I used an old parabolic satellite dish which was
unsuitable.
Scanning past antenna papers point to the use of a cone shape similar
to a horn of 2 metres diameter
produces better results. The antenna needs a longer mast so at the
moment I can't compare
F/R. Either way, with the radiator within the reflector envelope it is
difficult to understand what creates
a rearward lobe regardles of scale or frequency of use with respect to
receive. At the moment I see nothing that points away from the
Rutherford particle experiments with foil .ie penetration when at
right angles , deflection at other angles.

That antenna was when I used an old parabolic satellite dish which was
unsuitable.
Scanning past antenna papers point to the use of a cone shape similar
to a horn of 2 metres diameter
produces better results. The antenna needs a longer mast so at the
moment I can't compare
F/R. Either way, with the radiator within the reflector envelope it is
difficult to understand what creates
a rearward lobe regardles of scale or frequency of use with respect to
receive. At the moment I see nothing that points away from the
Rutherford particle experiments with foil .ie penetration when at
right angles , deflection at other angles.

As usual Art you are avoiding answering the questions and choose to confuse
the issues
with you own preconceived ideas and terminology. The fact that the feed is
totally within the "reflector envelope" tells you or us nothing about
sidelobes and edge taper.
I really don't think you want answers, but I'll try once mo
1. What frequency
2. What is the dish diameter
3. What is the dish focal length to diameter ratio (F/D)

Dale W4OP

On Apr 10, 6:00*pm, "Dale Parfitt" wrote:
*That antenna was when I used an old parabolic satellite dish which was
unsuitable.
Scanning past antenna papers point to the use of a cone shape similar
to a horn of 2 metres diameter
produces better results. The antenna needs a longer mast so at the
moment I can't compare
F/R. Either way, with the radiator within the reflector envelope it is
difficult to understand what creates
a rearward lobe regardles of scale or frequency of use with respect to
receive. At the moment I see nothing that points away from the
Rutherford particle experiments with foil .ie penetration when at
right angles , deflection at other angles.

As usual Art you are avoiding answering the questions and choose to confuse
the issues
with you own preconceived ideas and terminology. The fact that the feed is
totally within the "reflector envelope" tells you or us nothing about
sidelobes and edge taper.
I really don't think you want answers, but I'll try once mo
1. What frequency
2. What is the dish diameter
3. What is the dish focal length to diameter ratio (F/D)

Dale W4OP

I am not avoiding questions, just those that appear irrelevant, but
here goes Anything to make you happy, this should be interesting how
you use these answers with respect to the posted question

1 160 metres upto 2 metres, tunable

2 2 metres

3 Doesn't have a focal length, it is an end fed ( series connection)
helix antenna.

At least to the best of my knowledge which is why I posed the question
Hopefully we will all stay on subject and not get side tracked. I will
leave it to others to respond to Richard when they determine what he
is talking about.

On Fri, 10 Apr 2009 16:49:31 -0700 (PDT), Art Unwin
wrote:

1. What frequency
2. What is the dish diameter
3. What is the dish focal length to diameter ratio (F/D)

I am not avoiding questions, just those that appear irrelevant,

20 postings to get to the point (not unanticipated, however) which Art
calls "irrelevant."

As for those answers?
1 160 metres upto 2 metres, tunable

2 2 metres
Hence the wholesale disregard for first principles in size vs.
wavelength. Elementary analysis need not go any further when failure
is so obviously designed in.

3 Doesn't have a focal length, it is an end fed ( series connection)
helix antenna.
-Well, maybe not obvious to everyone.-

But why don't we chalk this design up to S U C C E S S and call it a
thread? If this bier gets anymore wreaths tossed onto it, it will
kill the pallbearers.

73's
Richard Clark, KB7QHC

On Apr 10, 7:19*pm, Richard Clark wrote:
On Fri, 10 Apr 2009 16:49:31 -0700 (PDT), Art Unwin

wrote:
1. What frequency
2. What is the dish diameter
3. What is the dish focal length to diameter ratio (F/D)

I am not avoiding questions, just those that appear irrelevant,

20 postings to get to the point (not unanticipated, however) which Art
calls "irrelevant."

As for those answers?

1 160 metres upto 2 metres, tunable
2 2 metres

Hence the wholesale disregard for first principles in size vs.
wavelength. *Elementary analysis need not go any further when failure
is so obviously designed in. *

3 Doesn't have a focal length, it is an end fed ( series connection)
helix antenna.

-Well, maybe not obvious to everyone.-

But why don't we chalk this design up to S U C C E S S and call it a
thread? *If this bier gets anymore wreaths tossed onto it, it will
kill the pallbearers.

73's
Richard Clark, KB7QHC

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
know what you are talking about and intent is to disrupt this thread
why on earth are you muttering about nothing at length? Simple
question has been posed and obviously you do not know the answers that
antenna engineering knowledge would provide as you are not an engineer
but a actor or actress by day and by night. My question remains
unanswered after all these posts.How do signals arrive or depart from
the rear of a dish or horn? We all know that you don't know the answer
but there are qualified engineers in this group who possibly doand
willing to share.

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
know what you are talking about and intent is to disrupt this thread
why on earth are you muttering about nothing at length? Simple
question has been posed and obviously you do not know the answers that
antenna engineering knowledge would provide as you are not an engineer
but a actor or actress by day and by night. My question remains
unanswered after all these posts.How do signals arrive or depart from
the rear of a dish or horn? We all know that you don't know the answer
but there are qualified engineers in this group who possibly doand
willing to share.

Your antenna has nothing to do with dish antennas, bu rather plane
reflectors (of which yours is way too small as Richard pointed out).
I know we cannot change your opinion or teach you anything- so I am out of
here.

Dale W4OP

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

On Fri, 10 Apr 2009 18:01:17 -0700 (PDT), Art Unwin
wrote:

The posting is about dishes not antennas.

Are you offering recipes now? How to fill a 3 quart mixing bowl with
an imperial gallon of secret-sauce? I can anticipate the amazed
posting of how surprised you would be to find you need a mop there
too.

73's
Richard Clark, KB7QHC

Art Unwin wrote:


I am not avoiding questions, just those that appear irrelevant, but
here goes Anything to make you happy, this should be interesting how
you use these answers with respect to the posted question

1 160 metres upto 2 metres, tunable

2 2 metres

3 Doesn't have a focal length, it is an end fed ( series connection)
helix antenna.

At least to the best of my knowledge which is why I posed the question
Hopefully we will all stay on subject and not get side tracked. I will
leave it to others to respond to Richard when they determine what he
is talking about.


While this provide some details regarding your antenna, it is not sufficient
for me to visualize it.

If one can't visualize what you are talking about, getting help with your
questions will be difficult.

You could try a simple experiment: Remove the active part of your antenna
and replace it with a dummy load. Leave the reflector/dish/whatever in
place. If you still pick up signals, then the antenna itself may not be the
problem.

By 'active part', I mean the helix antenna.

You have a web site, a link to a picture would help me understand what you
are doing.