On 9/27/2013 8:57 AM, Robert Bruninga wrote:
Why don’t we see simple ¼ wave 75 ohm lines used as a first step in matching a 140 Ohm Helix to 50 ohms?
In my limited experience, it's easier to diddle around with a strip of brass or copper at the feed end of the Helix..
For example:
http://www.amsat.org/amsat/articles/g3ruh/117.html
I remember building a 1/4 wave coaxial matching section out of a piece of copper pipe with brass rod down the center. I think it was from a design in the ARRL antenna book as published in the late '70's. It was a pain to build since I had to sand down the brass rod to get it to the right diameter, and I was never really sure how well it worked, since I did not have any antenna instrumentation at the time.
-Joe KM1P