It's actually short of an electrical half-wavelength, which gives it
about 300 ohms of series capacitive reactance. That reactance is then
cancelled by the inductive CM choke, leading to a lower CM path
impedance and increased braid current. The effect is most noticeable,
not when the braid is an electrical half-wavelength and the CM path
impedance is lowest, but when it has a significant reactive component
which may be offset by the choke impedance.
Even with 16ft of coax a Reactive choke will increase the braid current;
albeit the current is low to begin with.
The point is that most operators will never know what their braid
impedance will be; and it will likely be very different on different
bands. So the safe option is a CM choke with a high RESISTIVE impedance.
73,
Steve G3TXQ
Dr. Gerald N. Johnson wrote:
> Of course there's lots of current in the braid, you made it nearly a
> half wave long. Try the same experiment with that braid 16 feet long and
> you will find much less current because then its a quarter wave long
> terminated in a low impedance.
>
> 73, Jerry, K0CQ
>
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