Horn antenna

Hello, I write to you from spain, my knowledge very are limited. I want to construct to a funnel for a HF antenna (receiving single) the idea I have seen it in Holland, but nonprofit but information. Treatment to extend the gain of a radar intercept receiver.
The band that interests to me is the Ka 34.3
I have seen these photos:

www.flitsservice.nl/techniek/images/Image2_2.jpg

www.flitsservice.nl/techniek/images/Image7_2.jpg

(refresh or F5)

the antenna and a second outer tail cone that is fit in the antenna without disassembling. In this photo you can see the interior of the antenna, reason why the cone is not so great, because waveguide inner is but it sins?

http://www.forocoches.com/foro/attac...&stc=1

http://www.forocoches.com/foro/attac...hmentid=151951

My questions are the following ones, to see if you can help me:
- since he is outer and it does not touch the antenna (on the inside), connect it to ground? (the external part of the antenna is of plastic)
- the length of the funnel and dimensions, depend on the single frequency of recepci? or is applied that to greater, more gain?
- What that material to constructing? iron, brass, aluminum, plastic? the better material?

I hope that you can help me, thanks and a greeting.

Walker

I can't see the hyperlinks you wrote, please check if they are correct.
In any case for "funnel" (horn) type antenna, dimension are related to λ and desired gain.
The flare angle is beamwith dependent and generally 20 to 25 dBi horns have 5...20° semi-flare angle. The exact flare will be computed with a CAD.
Look for sabor.exe it's a free cad wrote by a spanish university.

Materials used to build horns are good conductive metals, like Cu, Al alloy, etc. but higher resistivity metals like brass, metallized plastics also may by used accepting a very little reduction of the efficiency.

thanks to answer Sergio, the Link sometimes is necessary to give him to update (f5) so that they work. They are correct and very important for the answer and so that you occur an idea of which I try to do

thanks and a greeting

walk

Added after 4 minutes:

1a photo is the original antenna. 2a photo is with the funnel. 3 and 4 photo is the antenna on the inside. I want to have bought the
solution "done" but they does not sell Spain.

thanks

walk

Added after 33 minutes:

I test the links in another pc and not work

please copy the link text in new explorer window and then work.

regards

walk