[hpsdr] Proposal for Loop Anntenna

Mon Jul 2 15:13:26 PDT 2007

Hello George,

Is it copperleaf? Or foil?  Foil might be thick enough.  What does your package say? 

At 20M you'd need copper 20 um thick...40M would be something like 30 um thick.  For the truly ambitious, you would need 50um thick for 160m.  (I would love to see someone make a 160M Frankenstein Torus...that would truly cause panic in the streets.)

A Styrofoam core is an interesting idea...I hadn't considered that.    It wouldn't be very durable, but it might be fun for experimentation.

I was planning some kind of sturdier internal frame...I only wanted to do this once...so I wanted it durable.

Please let me know if you try some experimenting on this.

Regards,

Kurt - ae6uj

----- Original Message ----
From: George Medakovich <George at Medakovich.com>
To: Kurt Loken <ae6uj at yahoo.com>
Cc: hpsdr at hpsdr.org
Sent: Monday, July 2, 2007 4:25:48 PM
Subject: Re: [hpsdr] Proposal for Loop Anntenna

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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