[Elecraft] KX3 & Chasing local HF noise sources

Jim Brown jim at audiosystemsgroup.com
Fri May 2 03:39:14 EDT 2014


On 5/1/2014 11:14 PM, K8JHR wrote:
> My friend in Germany is making a serious study of common mode noise on 
> OCF dipoles, and from his work I know you must bring the transmission 
> line away at a 90 degree angle

It's MUCH more than that. OCF (off-center-fed) antennas (dipole implies 
balance) are badly unbalanced, which places a very high common mode 
voltage across a common mode choke because of their high degree of 
imbalance, which tends to fry (destroy) the common mode choke with high 
power.

The OCF antenna is an idea whose time is LONG past. In that long past 
time, it offered a broadbanded solution that was "OK," but not great, 
and in that long past time, noise was much less of a problem. Sadly, 
noise is a BIG problem, and that makes OCF antennas a really bad idea.

73, Jim K9YC


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