Topband: RX Loops

K8LV1 at K8LV1 at
Mon May 17 13:01:48 EDT 2004

In the original posting by W8JI, he stated: "They (loops) are electric field 
dominant at distances over 1/8wl up until far field where they are no 
different." Ther real problem with this statement is that it is ambiguous, but I am 
not interested in arguing semantics. I chose to interpret it in the sense that 
makes it relevant to practical RX antennas, which is the real subject of 
interest here.

I stated, and PROVED, that when this loop is in the far field of the TX 
antenna (which we approximate as an illuminating plane wave) it indeed is very 
different than other antennas. Namely, it responds only to the magnetic component 
of that field. An electrical dipole would respond only to the electric 
component, and that is a significant difference. It can be used as the basis for 
enhanced designs which rely on selective shielding of the E or H component.

That is why one is called an electric dipole and the other a magnetic dipole. 
The names ARE significant because they are a good indication of the 
underlying EM activity that occurs and that is why experienced antenna theoreticians 
like to use them. Electric and magnetic dipoles are very different, but related, 
objects and have distinct properties. I interpreted Tom's remarks to refute 
this fact and objected to them on this basis. I continue to object unless he 
modifies or retracts the above citation  (".....they are no different".).

For those interested in deeper understanding of the multipole nature of 
radiation and antennas, I would suggest the classic basic EM textbook by Stratton, 
which lays it out pretty clearly.

Eric K8LV

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