Topband: Pixel Technologies Magnetic RX Loop

[Jim Brown]

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