On Mon, 13 Mar 2006 23:04:03 -0800, Roy Lewallen
wrote:


You're correct that a trap doesn't stop current -- or energy -- at the
trap. The lines on both sides couple with each other, allowing
substantial current to flow on the side away from the source. All the
trap does is guarantee a current null at some point. A quarter wave
away, a current maximum will occur. In fact, a trap can increase current
coupled into a wire if it breaks a formerly non-resonant wire into
pieces of which one or more are near resonance.

Thanks Roy,

Given that BPL band plans often have a link bandwidth of several MHz,
one wonders also about the effectiveness of a trap in compromising
depth of notch vs bandwidth. Perhaps the magic bullet is really a band
stop filter, I didn't look the patent up.

But no matter, it seems it serves more to organise the location of
standing waves rather than eliminate current past the trap.

Of course, we are all scratching our head about the technical elegance
or even feasibility of BPL (or lack of it, more to the point).

Owen
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