I thought Richard's statement that modeling would tell you about how the
design might perform, was good advice. If you use EZNEC, I'd be willing
to help you if you dont already know how to use it to model your antenna.

Jerry KD6JDJ


Jerry, thanks for the offert.
I dont know how good these modelling programs are in this situation.
But if it is easy, so could somebody do the following:

Take 20m of wire, that is half of a dipole.
Put a 1/4 electric wavelength shorted stub for 10,1MHz so that the open end
is 7,25m from center and the shorted end pointing to the tip of antenna. One
side of stub is the 20m wire itself, like in the upper picture. Ignore all
velocity factors to make it sinple.
Now tell me what are the resonance frequencies of that kind of element and
if possible feed point impedande (80m and 30m)

I know I could do it myself but as you know learning to use a new program
reliably takes lot of time.

73 Jouko OH5RM

On Wed, 16 Apr 2008 17:01:24 +0300, "JN" wrote:

Jouko, I noticed this thread took a detour, but I never saw anyone
actually try to answer your question. I too, am looking to see the
answer on this.

73 for now
Buck, N4PGW

www.lumpuckeroo.com

Yes Buck it is often difficult to get an answer just to the question you are
asking.
Anyway very soon all snow has melted away here and then its possible to
testbuild it.

73 Jouko OH5RM


Repeated message seeing that you both missed it:

On Tue, 15 Apr 2008 21:44:02 +0300, "JN" wrote:

I understand that you would suggest 90 degree?
But does it really matter?

Hi Jouko,

At right angles, yes. Does it matter? That depends on proximity to
other conductors, including itself if you "coil" it around the
radiator, or along the radiator.

When I looked at your first posting, I was confused by the single
wire, and the text graphics should have been done in fixed font.

Keep the line conductors at least 3, preferably more, wire diameters
from the radiator or themselves. Use the largest diameter for the
multiplier of 3 (or more).

73's
Richard Clark, KB7QHC

73's
Richard Clark, KB7QHC

Repeated message seeing that you both missed it:

73's
Richard Clark, KB7QHC

Hi Richard,

No everything red carefully.
I fully understand what you are suggesting.
Cutting the element and insertin stub at right angles
Sure works OK but that is no answer to my original question, HI

73 Jouko OH5RM

"JN" wrote in message
...
I am planning a two band antenna for 30 and 80m using linear traps.
The idea is to build the antenna of zip-cord type line 140ohm vf 0.73.
Trap is made using 1/4 wave shorted stub, decoupling occurs at the open
end.

Thanks to everybody for valuable comments.
Special thanks to Jim K7JEB, who made the simulation and verified that the
antenna
works as expected.

After much confusion with the text graphics, I learned the lesson to never
use them again

So here is how the antenna works
http://farm4.static.flickr.com/3078/...7c03acc4_o.jpg

I am going to use this kind of material, which is very commonly used by
telephone companies here.
http://www.saunalahti.fi/hohtola/ham/killu/killu.html

And here is how it will be made:

http://farm3.static.flickr.com/2072/...5653e9b9_o.jpg

Why not normal traps? Easier to build
Why not parallell dipoles? Much shorter
You get three bands if needed very easily

73 Jouko OH5RM