[hpsdr] Proposal for Loop Anntenna

[George Medakovich]

How about copper foil over a styrofoam core?
I picked up some copperleaf foil a while back to experiment with different
ways to make a low-weight microwave horn, but haven't gotten around
to actually trying it yet.  Copperleaf might be a bit thin for skin effect
at HF, though.

George Medakovich, ae5ci

Kurt Loken wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hello Ken,
> 
> What a great idea to have the computer keep the loop
> resonant while you tune your SDR!  SDR and Magloops
> seem like a great combo...especially for urban folks
> with space limitations like myself.  It is also kind
> of cool to think that even the antenna would, in a
> way, be software defined!
> 
> ...and now for something completely different...
> 
> Your proposal has stirred some not too distant
> memories...and here I thought I had put magloops
> behind me and reformed.
> 
> I've never actually made a magloop (nor told anyone
> this story other than my therapist), but the mad
> scientist in me wanted to make the greatest small
> magloop ever made...a true abomination to man!!! (Did
> I just cackle?) 
> 
> I may as well share my story of the Frankenstein Torus
> Magloop...
> 
> I once flirted with the idea of making a small loop
> that would be efficient (>90%) even down at 7MHz...yet
> still be relatively small (~6 feet in diameter).  I
> got very hung up on efficiency of the design, and this
> lead me down the path of the exotic (or, rather, the
> silly).  (AA5TB's calculator is really nice for trying
> out ideas/designs...and exploring the silly).  
> 
> One of the knobs you have for efficiency is conductor
> diameter.  I thought about using copper sheets
> soldered together over a hollow frame (sort of kind of
> reminiscent of paper mache).  The idea here was to
> take advantage of the skin effect.  The poor little
> naive electrons would think they were on the surface
> of a huge torus of solid copper!  I had considered
> making the diameter of my "copper mache" as big as 8
> inches.   The electrons would see a solid copper
> conductor that was 8 inches in diameter...bent into a
> loop with the diameter of 6 feet!  (Oh! To have
> actually built it and brought it into the world!!! 
> Hell, if it didn't work, I could have sold it as lawn
> art!)
> 
> Fortunately, I didn't have the time to actually try to
> make the Frankenstein Torus due to a move from Silicon
> Valley to lovely Minnesota (and due to a wife who was
> less than supportive of my grand idea), but I got to
> the point where I was scoping out materials.  
> 
> I planned to use a vacuum variable for the cap...and I
> had a reliable source lined up in the US.  (FYI, don't
> buy from Russia!!!  These things are very
> fragile...make sure you aren't buying broken
> crap...make sure you can get your money back if it is
> junk.)  
> 
> I wasn't sure about was how to best tapper the 8 inch
> torus diameter down to solder to the vacuum variable,
> but I do have ideas even now that haunt me on how I
> would actually do it and retain the skin effect and
> efficiency.
> 
> For the copper sheets, I considered using a roll of
> ordinary copper flashing like you could find at home
> depot.  
> 
> I also got to the point where I was designing the
> templates you would use to cut out 20 flat sheets of
> flashing to make a beautiful 20 segment copper torus
> when put over the inner frame. (To this day, I wonder
> how much solder it all would have taken.)
> 
> Hopefully, I can sleep tonight.
> 
> Thanks alot,  Ken. 
> 
>  Jeez.
> 
> Kurt - ae6uj
> 
> 
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