On 12/13/2019 10:49 AM, RT Clay wrote:
In ON4UN's book there is a description of a large feedline trap that can be
used to decouple a dipole. Basically you have the dipole feedline wound in a
large air-wound coil (4 inch sewer pipe) resonated by a capacitor. I am using
this to decouple the 80m dipole on my tower.
This is a high-Q equivalent to the low Q of a well-designed ferrite
choke. http://k9yc.com/2018Cookbook.pdf The ferrite choke typically has
a circuit Q on the order of 0.5, making it quite broadband. That low Q
value is the result of loss coupled from the ferrite core, so a
well-designed choke must limit common mode current so that there is no
over-heating. More conceptual explanation is in k9yc.com/RFI-Ham.pdf and
in the ARRL Handbook.
73, Jim K9YC
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