[hpsdr] Proposal for Loop Anntenna

[Kurt Loken]

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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