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Old July 9th 17, 03:29 PM posted to rec.radio.amateur.antenna
John S John S is offline
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First recorded activity by RadioBanter: May 2011
Posts: 540
Default Magnetic receiving loop theory

On 7/9/2017 8:08 AM, Pat wrote:

I'm looking at an ad in QST regarding the MFJ Low-Noise Receiving
Loop. Since I have a lot of noise here, I am very interested in this
topic. However, I have having trouble understanding the theory. My
understanding regarding electromagnetic waves is you can't have one
without the other. RF propogates through space my having the moving
electric field create a moving magnetic field which then creates a new
electric field, etc, etc. How can one exist without the other?


You are correct, they can't.

Here's a quote from the ad, "The MFJ-1886 drastically reduces noise
and interference by receiving the magnetic field and rejecting the
electric field". How can a varying electric field from a noise source
not also create a corresponding magnetic field? Is this a near-field
/ far-field thing?


Pat


I seem to recall that within a couple of wavelengths, there is a
difference in the magnetic and electric fields and the magnetic field
diminishes rapidly beyond that but remains associated with the electric
field as you say.

I have read trusted authors who say that the real value in a small loop
is the ability to null the incoming interference.

MFJ is lacking in technical knowledge. They said that my MFJ analyzer
would measure impedance (Z). It does not measure the imaginary part. It
measures absolute value of impedance (|Z|).

Cheers,
John