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Topband: Mobius shielded loop

To: topband@contesting.com
Subject: Topband: Mobius shielded loop
From: Herb Schoenbohm <herbs@vitelcom.net>
Reply-to: herbs@vitelcom.net
Date: Mon, 09 May 2011 12:06:54 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Andy Ikun, G8LUG wrote in part........
>
>
> Notwithstanding the above. A Mobius shielded loop was constructed using 
> 38inch diam. aluminium tube, 3/4inch OD with a split at the top of the loop, 
> the inner wire was made from the outer braid of RG58c. This loop is 
> effectively 2 turns with a loop inductance of 10uH (res. freq is 5.1MHz). 
> This compares to 2.2uH for a 1 turn loop with above size of tube (Res. 
> Freq.>50MHz).
>
> The net result was that below 18MHz any gain difference was only due to 
> differences in the loop to amplifier match.
>
> Between 18MHz and 30MHz the gain of the Mobius drops off significantly by up 
> to 12dB due to the very high loop capacitance.
>
> Both loops had identical nulls.
>
> As far as can see; there is no technical reason to use a Mobius loop for a 
> broadband antenna.
>
>
>
>
>
If there is any advantage for a 1.8 Mhz resonance with enhanced capture 
area while retaining the special loop nulling characteristics, would it 
not make sense to build a  bigger loop?

After putting "Mobius" in Google I became even more fascinated to read 
that J.S. Bach and Nikola Tesla, both geniuses in their own fields, were 
intrigued by the Mobius configuration.  I saw where a device called a 
Mobius resistor is an electronic circuit element which has the property 
of canceling its own inductive reactance. Tesla patented similar 
technology in the early 
1900s:^<http://en.wikipedia.org/wiki/M%C3%B6bius_strip#cite_note-8> 
"Coil for Electro Magnets" was intended for use with his system of 
global transmission of electricity without wires. Bach wrote several 
Mobius canons that are even more fascinating than the paper strip in art 
class.  Bach was great at composing "unenliche" melodies where the end 
is the beginning and the beginning is the 
end.^<http://en.wikipedia.org/wiki/M%C3%B6bius_strip#cite_note-10>

In electronics Mobius considerations appear as:

    * as compact resonators with the resonance frequency which is half
      that of identically constructed linear
      coils^<http://en.wikipedia.org/wiki/M%C3%B6bius_strip#cite_note-11>
    * as induction-less
      resistance^<http://en.wikipedia.org/wiki/M%C3%B6bius_strip#cite_note-12>

    * as superconductors with high transition temperature

My questions are:

(1)  would not  Mobius theory be applicable to cancelling out  inductive 
reactance in antenna feed systems such as shunt fed towers or shortened 
vertical radiators?

(2) would not a larger sized Mobius loop provide deep nulls but with a 
higher gain at 1.8 Mhz yet small enough to allow rotation by a 
conventional TV rotators?

Maybe this water has gone over the dam long ago but I am curious if 
there is anything there to consider.


Herb, KV4FZ


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