Topband: Thanks!

[Jim Brown]

On 5/21/2013 1:18 PM, ZR wrote:
> Are you now claiming that the thousands of bead choke baluns in use 
> for decades at HF and 6M dont work?

I have published extensively on this, first in 2005 in a peer reviewed 
AES paper, and later in my RFI tutorial. All of this work is on my 
website.  W1HIS published his work on this in 2006. A few years ago, an 
engineering supervisor at CIA sent me work from an US Army research 
group prepared in the 70s reaching the same conclusions as I had.  And 
literature searches for my AES paper found references (in a European 
ferrite manufacturer's applications notes) to the importance of 
resistance in chokes as far back as the 50s.

> I suspect that those who have been happy with the results in mimizing 
> feedline radiation would heartily disagree.... 

Many people believe many things that are not true. Many false beliefs 
are based on a grain of truth. The generalized assumption in ham 
literature has been that 500 ohms choking Z is sufficient to prevent 
pattern distortion caused by feedline radiation, but W1HIS showed that 
increasing choking Z to the range of 5,000 ohms can significantly reduce 
receive noise. When I saw his paper, I immediately tried multi-turn 
chokes on an antenna that was picking up a lot of noise. The choke 
reduced the noise by nearly 10 dB. Since I published my work, hundreds 
of hams have told me they have had similar results.

73, Jim K9YC