At 09:43 AM 8/20/2007, SV1BSX wrote:
Hi Tony,
Thanks for publishing of your "Para-Lindy", definitely your arrangement solved all difficulties and puzzles from the previous complicated designs. Its quite simple now and easy to make it, for anybody. My compliments for your clever design.
Just a question:
Why not the coaxial-feeder inside of down-part dipole's tube (as sleeve) but outside of this?
Thanks again for publishing.
73 de Mak, SV1BSX
Hi Mak,
Thanks for your interest!
When I was working on this last year, I had a lot of trouble getting consistent performance using a sleeve BALUN (i.e. with the coax running down the center) so I came up with the ferrites as an alternative. Just running the coax down the center is not sufficient to decouple the feed from the antenna. Whats more, I want the antenna to be very easy to build using standard plumbing parts and not require any machined parts or require any high-precision work to get good results. This means it needs to have a wide bandwidth.
But, I have continued working on this antenna and hope to have a new version to present at the 2007 AMSAT-NA Space Symposium that will in fact use a sleeve BALUN instead of the ferrites.
The trick is to use a very thin coax cable along with the plumbing parts that dielectrically load the sleeve so that the resulting BALUN presents a high decoupling impedance across a wide bandwidth. This eliminates the need for tuning or high-precision work.
I am still finalizing the design but with a little luck I will have it for the October Symposium.
73, Tony AA2TX