[UK-CONTEST] Current transformers on vertical antennas

[Ian White GM3SEK]

G3SJJ wrote:
>I am just about to start a rebuild of my phased pair of verticals for
>40m plus also add a 5/8w for 30m with an increased emphasis on
>efficiency. In the past I have experienced RF feedback on 40m SSB and
>wondered if part or all of the problem is lack of current chokes where
>the feedlines connect to each element. To this end I have decided to
>anyway add chokes.
>
>ON4UN's Low Band Dxing suggests using between ten and thirty 43-1024
>beads which will slip over RG213. I guess I could look at the data sheet
>but wondered if anyone had an instant answer to the optimum number for
>7MHz and also 10.1MHz?
>

Nobody else can guess how many beads you will need. (You'd need to give 
a lot more information, and still the answer would be guesswork.)

Here is a link to a simple RF current meter that you can build out of 
the junk box in half an hour. Clamp that over the coax and you'll start 
to get some real answers.

http://www.ifwtech.co.uk/g3sek/clip-on/clip-on.ppt  (1.5MB)

(Adapted from Saturday's GMDX talk - guaranteed no "animation" this 
time, chaps  :-)


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek