Reflector mesh surface
 

"Art Unwin" wrote in message
...
Since we are at the low sun cycle I shoose
1" hexigon poultry wire for the mash on my 3 metre dish
At what frequency will there be a noticable effect on aperture
starting with top band?
Many thanks
Art KB9MZ...,XG

where did art go??? i need a good laugh!

Reflector mesh surface
 

Dave wrote:

"Art Unwin" wrote in message
...
Since we are at the low sun cycle I shoose
1" hexigon poultry wire for the mash on my 3 metre dish
At what frequency will there be a noticable effect on aperture
starting with top band?
Many thanks
Art KB9MZ...,XG

where did art go??? i need a good laugh!


Hopefully for treatment.



--
Jim Pennino

Remove .spam.sux to reply.

Reflector mesh surface
 

Dave wrote:

where did art go??? i need a good laugh!


Co-dependent, eh?

- 73 de Mike N3LI -

Reflector mesh surface
 

"Dave" wrote in message
...

"Art Unwin" wrote in message
...
Since we are at the low sun cycle I shoose
1" hexigon poultry wire for the mash on my 3 metre dish
At what frequency will there be a noticable effect on aperture
starting with top band?
Many thanks
Art KB9MZ...,XG

where did art go??? i need a good laugh!

art deco?

mary xmas

Reflector mesh surface
 

On Dec 25, 10:58*am, "KC8QJP" wrote:
"Dave" wrote in message

...

"Art Unwin" wrote in message
...
Since we are at the low sun cycle I shoose
1" hexigon poultry wire for the mash on my 3 metre dish
At what frequency will there be a noticable effect on aperture
starting with top band?
Many thanks
Art KB9MZ...,XG

where did art go??? *i need a good laugh!

art deco?

mary xmas

Update
I have made the dish using 1 inch poultry fencing.
The outline of the dish encloses the backfire antenna i.e. the
antenna finishes at the same datum line
as the periphery of the dish. The reason for this is that I am trying
to obtain a zero plus take off angle or
something less than normal with respect to frequency and height using
a planar design
Placed dish on ground with beam pointing upwards and did a swr graph
from 2 to 20 mhz
Repeated above except dish placed at right angles to earth.
Swr for 14 meg hz rose from 2:1 to 3: 1 but both arrangements followed
the same oscillation of SWR.
Difference probably due to variation in dish efficiency.i.e the first
set up was augmented by the ground surface.,
Haven't added the band frequency selection points as yet.
With the graphed impedance curves being similar I am anticipating a
TOA of around
5 degrees when antenna is raised to around 30 feet
Antenna polarisation is horizontal, verticle and cw cwith respect to
gain polarization all being equal in gain, with total gain
being close to 2.5 db in excess of the other polarizations.
As I stated ,the idea is to lower the TOA from that of a normal planar
design.
Comments welcome as well as thrown rocks and sarcasm. I have modeled
this type of antenna pointing straight up
but not in a horizontal plane which is why I was able to sugest gain
comparables.
Regards
Art

Reflector mesh surface
 

"Art Unwin" wrote in message
...

totally worthless bull snipped

thanks art, i needed that. i'd like to see how you do running qrp in the
stew perry contest this weekend.

Reflector mesh surface
 

On Dec 27, 5:14*am, "Dave" wrote:
"Art Unwin" wrote in message

...

totally worthless bull snipped

thanks art, i needed that. *i'd like to see how you do running qrp in the
stew perry contest this weekend.

Well the idea of 1 inch mesh was a bum idea. I should have kept to my
own thinking.
When transmitters have holes in the casing of 1 inch diameter will be
the time I will use such large holes.
Will now have to take it of and replace with aluminum window mesh.
The present mesh has no idication of working in any sence of the word
Art

Reflector mesh surface
 

"Art Unwin" wrote in message
...

Well the idea of 1 inch mesh was a bum idea. I should have kept to my
own thinking.
When transmitters have holes in the casing of 1 inch diameter will be
the time I will use such large holes.
Will now have to take it of and replace with aluminum window mesh.
The present mesh has no idication of working in any sence of the word
Art

let me give you a hint... its not the mesh that is the problem.

Reflector mesh surface
 

"Dave" wrote in message
...

"Art Unwin" wrote in message
...

Well the idea of 1 inch mesh was a bum idea. I should have kept to my
own thinking.
When transmitters have holes in the casing of 1 inch diameter will be
the time I will use such large holes.
Will now have to take it of and replace with aluminum window mesh.
The present mesh has no idication of working in any sence of the word
Art

let me give you a hint... its not the mesh that is the problem.


The theoretical gain of a dish is expressed as (9.87 times D-squared) /
(wavelength-squared), where D is the dish diameter. If you have a 3 meter
dish and you're working 10m, I calculate the gain as less than unity. Ref:
http://en.wikipedia.org/wiki/Parabolic_antenna

Even then, the efficiency of the dish is assumed to be 100% -- which it
never is. One limitation is the effectiveness of illuminating the entire
surface of the dish uniformly. How can you do that at HF? You need a
compact illuminator at the focal point of the dish but HF doesn't lend
itself to such gyrations.

I think you should not consider a dish for HF. It works only for
wavelengths that are small, compared to the dish size. Don't fight the
math.

Reflector mesh surface
 

"Sal M. Onella" wrote in message
...

"Dave" wrote in message
...

"Art Unwin" wrote in message
...

Well the idea of 1 inch mesh was a bum idea. I should have kept to my
own thinking.
When transmitters have holes in the casing of 1 inch diameter will be
the time I will use such large holes.
Will now have to take it of and replace with aluminum window mesh.
The present mesh has no idication of working in any sence of the word
Art

let me give you a hint... its not the mesh that is the problem.


The theoretical gain of a dish is expressed as (9.87 times D-squared) /
(wavelength-squared), where D is the dish diameter. If you have a 3 meter
dish and you're working 10m, I calculate the gain as less than unity.
Ref:
http://en.wikipedia.org/wiki/Parabolic_antenna

Even then, the efficiency of the dish is assumed to be 100% -- which it
never is. One limitation is the effectiveness of illuminating the entire
surface of the dish uniformly. How can you do that at HF? You need a
compact illuminator at the focal point of the dish but HF doesn't lend
itself to such gyrations.

I think you should not consider a dish for HF. It works only for
wavelengths that are small, compared to the dish size. Don't fight the
math.



what do you get for gain when you use it on 160m like art is doing?