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
All good topband ops know how to put up a beverage at night.
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Topband Reflector
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