On 5/9/2011 3:27 PM, W2PM wrote:
> The mag loop can only be sensitive go the magnetic field and less so to the E
> field only if it is very very close to noise source. That's just the way
> Nature works.
Yes. To clarify, the magnetic field dominates in the near field of a
current source, and the electric field dominates in the near field of a
voltage source. In the far field the magnetic and electric fields are of
equal import, and are related by the impedance of free space.
The transition from near field to far field is gradual, and for A POINT
SOURCE, begins at roughly one-sixth wavelength. For larger and more
complex sources, the transition may be at a far greater distance. Doing
the math is instructive. At 160M, 1/6 wavelength is 350 ft. Many noise
sources are NOT point sources.
In general, a loop that did not respond to the electric field would be
most effective at rejecting a nearby impulsive source, like an arcing
insulator or neon sign. As has been noted, this behavior is completely
separate from the ability of the loop to produce a null. And once you
get into the far field, the null is all you have going for you.
73, Jim K9YC
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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