Loading coils: was Dish reflector
 

Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic.

So what? An ever increasing Z0 does not change the
basic characteristics of a standing wave antenna, one
characteristic of which is: The phase of the current
relative to the feedpoint current phase changes by
a minuscule amount. So exactly how did you use that
current to measure and calculate delay???

I've never seen an attempt at
simulating it with distributed resistance, ...

Then, just as I suspected, you have never looked at my
web pages. Radiation "loss" can easily be simulated by
resistance wire. Please download

http://www.w5dxp.com/stub_dip.EZ

and alleviate your ignorance.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Loading coils: was Dish reflector
 

On Apr 22, 11:58*am, Cecil Moore wrote:
Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic.

So what? An ever increasing Z0 does not change the
basic characteristics of a standing wave antenna, one
characteristic of which is: The phase of the current
relative to the feedpoint current phase changes by
a minuscule amount. So exactly how did you use that
current to measure and calculate delay???

I've never seen an attempt at
simulating it with distributed resistance, ...

Then, just as I suspected, you have never looked at my
web pages. Radiation "loss" can easily be simulated by
resistance wire. Please download

http://www.w5dxp.com/stub_dip.EZ

and alleviate your ignorance.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Anybody got a copy of the two articles that Roy alluded too
I would really like to read them
Regards
Art

Dish reflector
 

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

Loading coils: was Dish reflector
 

Cecil Moore wrote:
Jim Kelley wrote:

I have the same recollection as Tom.

If you do, it was from many years ago when I was young
and foolish. :-)

Evidently some things never change. :-)

ac6xg

Loading coils: was Dish reflector
 

Jim Kelley wrote:
Evidently some things never change. :-)

The thing that never changes is that you always
remember to dredge up the worst about someone
even if it happened 10 years ago. Have you
always been perfect?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

Art Unwin wrote:

The helix is four foot long and a foot diameter. The base of the
reflector is 1.5 feet
snip
Art

A 1 foot diameter helix would be a design for the 1 meter band, not 160.
You need to scale it up just a bit.

The diameter should be about 50 meters. The reflector should be maybe
150 meters in diameter. This is not going to fit in your back yard.

tom
K0TAR

Dish reflector
 

On Apr 22, 8:46*pm, Tom Ring wrote:
Art Unwin wrote:

The helix is four foot long and a foot diameter. The base *of the
reflector is 1.5 feet
snip
Art

A 1 foot diameter helix would be a design for the 1 meter band, not 160.
* You need to scale it up just a bit.

The diameter should be about 50 meters. *The reflector should be maybe
150 meters in diameter. *This is not going to fit in your back yard.

tom
K0TAR

Tom
What you say it should be is guided by conventional teachings and my
designs are not conventional. Per conventional teachings it would be
very large indeed which is why my design has to be different Actually
I want to see if I can lower the conventional take of angle with the
use of tipping mechanism plus the rotator addition.
With CP I may lose a bit of S meter readings but if I can lower the
TOA with the antenna on the ground that will be a big step forward.
Any way the antenna doesn't know that it should not work and despite
your comments it works OK, but as yet I have not been able to
establish the radiation patterns. So I have a antenna at around 30
feet and the other on the ground with a tipping device so the up
coming tests should be interesting.
Both antennas will cover top band and of course will have gain, but at
the moment it is TOA that I am concentrating on, after that it is
patterns
It is the journey not the destination.
Regards
Art

Dish reflector
 

Art Unwin wrote:
On Apr 22, 8:46 pm, Tom Ring wrote:
Art Unwin wrote:

The helix is four foot long and a foot diameter. The base of the
reflector is 1.5 feet
snip
Art
A 1 foot diameter helix would be a design for the 1 meter band, not 160.
You need to scale it up just a bit.

The diameter should be about 50 meters. The reflector should be maybe
150 meters in diameter. This is not going to fit in your back yard.

tom
K0TAR

Tom
What you say it should be is guided by conventional teachings and my
designs are not conventional. Per conventional teachings it would be
snip
Art

Ok. So what have you changed from a standard helical design that makes
it "not conventional" ?

Your original description sounded pretty much like a stock 1m band
helical, so if you've done something to pull it down 160:1 in frequency,
I'd love to hear what it is. It must be simple and obvious, because you
didn't mention it in your post.

tom
K0TAR

Dish reflector
 

Tom Ring wrote:snip
Tom
What you say it should be is guided by conventional teachings and my
designs are not conventional. Per conventional teachings it would be
snip
Art

Ok. So what have you changed from a standard helical design that makes
it "not conventional" ?

Your original description sounded pretty much like a stock 1m band
helical, so if you've done something to pull it down 160:1 in frequency,
I'd love to hear what it is. It must be simple and obvious, because you
didn't mention it in your post.

tom
K0TAR

Oh, I forgot.

Art, you need to google for "axial mode".

tom
K0TAR

Dish reflector
 

On Apr 22, 10:59*pm, Tom Ring wrote:
Tom Ring wrote:snip
Tom
*What you say it should be is guided by conventional teachings and my
designs are not conventional. Per conventional teachings it would be
snip
Art

Ok. *So what have you changed from a standard helical design that makes
it "not conventional" ?

Your original description sounded pretty much like a stock 1m band
helical, so if you've done something to pull it down 160:1 in frequency,
I'd love to hear what it is. *It must be simple and obvious, because you
didn't mention it in your post.

tom
K0TAR

Oh, I forgot.

Art, you need to google for "axial mode".

tom
K0TAR- Hide quoted text -

- Show quoted text -

I tried to tell Art this but he just told me Krauus was wrong.

Jimmie