On Apr 11, 3:58*am, Helmut Wabnig hwabnig@ .- --- -. dotat wrote:
On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin



wrote:
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

How do you know?
The "rear" signals may come from the front side actually, having
been reflected by your neighbours house, or distant mountains,
or anything in between.

w.

Helmut
I do not know if the rear signals were as you suspected.,
It is extremely windy here in the midwest for the last few days
so I took off the new dish of it's ground stand and placed the dish in
a corner outside the house with a TOA that I assume is about 10-15
degrees. Again I got rear signals
but I noticed the coverage was very narrow and maybe more than one.
So next two weeks or so I will repeat the test but also play around
with the elevation
to see if there are other observables to determine if you are correct.
I am playing with circular polarisation which is a new experience for
me and I believe that is capable of picking up reflections that one
does not normally see with planar designs
Best regards
Art

On Apr 26, 5:10*pm, Art Unwin wrote:
On Apr 11, 3:58*am, Helmut Wabnig hwabnig@ .- --- -. dotat wrote:



On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin

wrote:
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

How do you know?
The "rear" signals may come from the front side actually, having
been reflected by your neighbours house, or distant mountains,
or anything in between.

w.

Helmut
I do not know if the rear signals were as you suspected.,
It is extremely windy here in the midwest for the last few days
so I took off the new dish of it's ground stand and placed the dish in
a corner outside the house with a TOA that I assume is about 10-15
degrees. Again I got rear signals
but I noticed the coverage was very narrow and maybe more than one.
So next two *weeks or so I will repeat the test but also play around
with the elevation
to see if there are other observables to determine if you are correct.
I am playing with circular polarisation which is a new experience for
me and I believe that is capable of picking up reflections that one
does not normally see with planar designs
Best regards
Art

Helmut. Re original thread on dish

I found out what the problem was! The dish itself was in the antenna
circuit thus
the dish was part of the antenna and receiving omni.ie chassis and
ground was the same connection I have discarded the dish experiment
and have gone back to the original design roots.
I can hold it up on one hand stretched out without problems and not
only is it light but also small. Have placed a small cctv rotator and
tipper on a table outside and am now setting up the controls. I
suppose I will have to add a decoder to the motors at a later date so
I can determine positions to follow the band conditions as they
change I do not have a direction indicator so I will wait for a warm
day where I can operate it and seethe position at the same time. The
tipping action will give me control of the skip distance so that
should prove to be very interesting. Anyway, glad that I now have
direction ability back. Tks for your interest.
Regards
Art

"Art Unwin" wrote in message
...
I found out what the problem was! The dish itself was in the antenna
circuit thus the dish was part of the antenna and receiving omni.

DOH!

I have discarded the dish experiment

AWWW, i would have loved to have a rotatable dish for 160m!

On Apr 29, 6:10*pm, "Dave" wrote:
"Art Unwin" wrote in message

...

I found out what the problem was! The dish itself was in the antenna
circuit thus the dish was part of the antenna and receiving omni.

DOH!

I have discarded the dish experiment

AWWW, i would have loved to have a rotatable dish for 160m!

David I still have that rotatable form for top band! I just gave up on
large dish experiments! As I stated I like the idea of small and light
antennas so I am keeping to those root desires. I am getting older so
the idea of climbing towers has to be adressed. Thus as an engineer I
solved that problem, now antennas where the height is not a necessity
for low take off angles! I now have to find out what the greatest
distance can be by substituting one skip for the presently used two
skips ie min TOA.
Since there are not the usual sun spots one has to be inovative and
devise means around it. I can still add a dish ofcourse but I like the
idea of a pencil beam as it will add more gain to that single skip
action. You really should get off that couch and figure out how you
are going to handle a poor sun spot cycle. My cctv rotator will never
be able to handle such a design when tipping is required as the weight
would overcome the motor and it would point into the ground, they are
built for just a small camera not a tank. By the way the antenna is
good for 2 meg upto 170 meg which are the range limits of my MFJ 259
meter. My guess is that it is good for broadcast band upto a giga or
more. Did you fall down?
Best regards
Art
Regards
Art

On Wed, 29 Apr 2009 23:10:03 GMT, "Dave" wrote:

"Art Unwin" wrote in message
...
I found out what the problem was! The dish itself was in the antenna
circuit thus the dish was part of the antenna and receiving omni.

On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin
wrote:
No baluns are used

That alone is at least one thing wrong with the design.

Three weeks and 300 messages ignored to discover first principles were
violated.

Is this discovery in time for this year's NoBell prize?

73's
Richard Clark, KB7QHC

*** Exordium ***
My dear Artifice, knowing your attachment to the practices of time out
of mind as indulged by the hooded monks whipping religion into their
young charges; I took a special effort to prepare you a debate with it
demarked by the classic degrees that you will note in *** stars ***

*** accumulatio ***
I have no experience with dishes
This is our first clue which you then elaborate with:
Rutherford of the UK ( Manchester)showed that particles could
piece a foil of gold
Your dish is of inferior craftmanship in that it is certainly not
gold:
The reflector is made from 1/2" mesh steel with an aluminum foil liner

*** Narratio ***
One would note that there is a world of antennas made with neither
gold, nor aluminum (isn't it aluminium?) foil, but thinner metal foil
on mylar or plastic. They work fine and do not suffer failure such as
yours. It would seem they are Rutherford partical resistant and do
not conform to your theory of a weekend farce. This is no surprise as
Margaret Rutherford was an English actress who played in the
flamboyant Oscar Wilde's "The Importance of Being Earnest." Your
work, as disappointing as it is does qualify as being earnest.

*** Divisio ***
However, one must observe the cautionary tale that inhabits that more
important (than your) work of Wilde's:

Jack - My dear Algy, you talk exactly as if you were a dentist.
It is very vulgar to talk like a dentist when one isn't a dentist.
It produces a false impression.

One could insert "antenna designer" for "dentist" to the same effect.
As for your fond attachment to Margaret Rutherford, let us take a leaf
from the script where she appears in full character of Miss prism:

Lady Bracknell - Is this Miss prism a female of repellent aspect,
remotely connected with education? It contained the manuscript of
a three-volume novel of more than usually revolting
sentimentality.

Miss prism - [grows pale and quails. She looks anxiously round as if
desirous to escape.]

*** Confirmatio ***
Let's see, Oscar Wilde wrote this at the end of the 19th century,
where much of your reading has been stalled in arrested development.
There is a reference to large written works (three volumes). The
implication being offered is such rambling work can be easily summed
up as the usually revolting sentimentality. And it is all brought
together in the character played by Margaret Rutherford. It shouldn't
take a leap of intelligence to note her character name of prism, and
the work done with prisms by Newton.

*** Peroratio ***
I was surprised to hear signals from the rear!

Lady Bracknell - This noise is extremely unpleasant.
It sounds as if he was having an argument.
I dislike arguments of any kind.
They are always vulgar, and often convincing.

73's
Richard Clark, KB7QHC

On Apr 12, 3:09*pm, Richard Clark wrote:
*** Exordium ***
My dear Artifice, knowing your attachment to the practices of time out
of mind as indulged by the hooded monks whipping religion into their
young charges; I took a special effort to prepare you a debate with it
demarked by the classic degrees that you will note in *** stars ***

*** accumulatio ***I have no experience with dishes

This is our first clue which you then elaborate with:Rutherford of the UK ( Manchester)showed that particles could
piece a foil of gold

Your dish is of inferior craftmanship in that it is certainly not
gold:

The reflector is made from 1/2" mesh steel with an aluminum foil liner

*** Narratio ***
One would note that there is a world of antennas made with neither
gold, nor aluminum (isn't it aluminium?) foil, but thinner metal foil
on mylar or plastic. *They work fine and do not suffer failure such as
yours. *It would seem they are Rutherford partical resistant and do
not conform to your theory of a weekend farce. *This is no surprise as
Margaret Rutherford was an English actress who played in the
flamboyant Oscar Wilde's "The Importance of Being Earnest." *Your
work, as disappointing as it is does qualify as being earnest.

*** Divisio ***
However, one must observe the cautionary tale that inhabits that more
important (than your) work of Wilde's:

Jack - My dear Algy, you talk exactly as if you were a dentist.
* * * * It is very vulgar to talk like a dentist when one isn't a dentist.
* * * * It produces a false impression.

One could insert "antenna designer" for "dentist" to the same effect.
As for your fond attachment to Margaret Rutherford, let us take a leaf
from the script where she appears in full character of Miss prism:

Lady Bracknell - Is this Miss prism a female of repellent aspect,
* * * * remotely connected with education? *It contained the manuscript of
a three-volume novel of more than usually revolting
* * * * sentimentality.

Miss prism - [grows pale and quails. She looks anxiously round as if
* * * * desirous to escape.]

*** Confirmatio ***
Let's see, Oscar Wilde wrote this at the end of the 19th century,
where much of your reading has been stalled in arrested development.
There is a reference to large written works (three volumes). *The
implication being offered is such rambling work can be easily summed
up as the usually revolting sentimentality. *And it is all brought
together in the character played by Margaret Rutherford. *It shouldn't
take a leap of intelligence to note her character name of prism, and
the work done with prisms by Newton.

*** Peroratio ***

I was surprised to hear signals from the rear!

Lady Bracknell - This noise is extremely unpleasant.
* * * * It sounds as if he was having an argument.
* * * * I dislike arguments of any kind.
* * * * They are always vulgar, and often convincing.

73's
Richard Clark, KB7QHC

This thread is hilarious ROTFLAMO . I just cant figure who is the
comic and whio is the straight man.

Welcome back Art, You may know nothing of antennas but you are
certainly the master of tolls.


Jimmie

Art Unwin wrote:
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

What's the relative size of "reflector" and helix? (i.e. is the
reflector in the near field of the helix, in which case, you could
easily have waves propagating along the surface of the reflector)

On Apr 20, 7:28*pm, Jim Lux wrote:
Art Unwin wrote:
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

What's the relative size of "reflector" and helix? *(i.e. is the
reflector in the near field of the helix, in which case, you could
easily have waves propagating along the surface of the reflector)

The helix is four foot long and a foot diameter. The base of the
reflector is 1.5 feet
with a 45 degree angle. I have had the helix 0.5 feet shorter and 0.5
feet longer with similar results.On re examination of the antenn I now
see that the ground lead of the radiator is connected to the inside of
the reflector at a half way point and the coax
ground is connected at the base of the reflector. I think I will
change that ground connection to a common point.
Regards
Art

On Apr 20, 8:43*pm, Art Unwin wrote:
On Apr 20, 7:28*pm, Jim Lux wrote:



Art Unwin wrote:
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

What's the relative size of "reflector" and helix? *(i.e. is the
reflector in the near field of the helix, in which case, you could
easily have waves propagating along the surface of the reflector)

The helix is four foot long and a foot diameter. The base *of the
reflector is 1.5 feet
with a 45 degree angle. I have had the helix 0.5 feet shorter and 0.5
feet longer with similar results.On re examination of the antenn I now
see that the ground lead of the radiator is connected to the inside of
the reflector at a half way point and the coax
ground is connected at the base of the reflector. I think I will
change that ground connection to a common point.
Regards
Art

Changing the ground point did not clear up the reception from the
rear!
Have made a smaller antenna ( not for top band) and mounted on a
framework on the ground. Same thing happening but band does seem
squirrily!
Have put a tilt mechanism on it and I am working on putting a rotator
on it so that I can get a better feel on things. I was going to do
this anyway as I want to see what this arrangement has on TOA. If
radiation is a matter of charged particles then penetration of dish
would change the direction of gain.....food for thought
The group can now go back to the subject of change
Regards
Art