On 1/20/11 12:54 AM, Steve Hunt wrote:
> For me, distortion of the radiation pattern of a simple dipole or loop
> is the very least problem that CM currents can cause.
>
> Much more significant is the potential for RFI, and increased noise
> levels on Rx, because the feedline has become an active element of the
> antenna system. It's usually easy to spot if you have the RFI problem;
> but the Rx noise problem is more difficult to identify, and many folk
> are unaware that they could potentially lower their noise levels by
> addressing the CM issue.
>
>
Well.. I see that as part of the pattern problem (albeit more a near
field than a far field pattern thing)...
That is, your feedline (and other surrounding conductors) become part of
the antenna. RFI is an issue because you're radiating from pieces that
are closer than you thought and noise because you've got gain where it's
unexpected (either due to close distance or because of a funky lobe in
the pattern)
Either way, chokes on the feedline DO help, but it's a bit tough to put
chokes on rain gutters, metal fences and roofs, etc.
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