[TowerTalk] making air wound coils (was Johnson Matchbox coil)

Roger (K8RI) K8RI-on-TowerTalk at tm.net
Sun Jul 27 20:00:35 EDT 2008

Rob Atkinson wrote:
> One of the ham magazines, either CQ or QST (but I'm pretty sure it was
> CQ) had a good article with photos a month or three ago on how to make
> your own air wound coils, including how to fabricate the spacers.  If
> you can get access to CQ for the past six months (i.e. if you know
> someone who subscribes) go through them and it should be in there.
I always figured if it had spacers, like the plastic strips in "Air dux" 
it wasn't really "air wound", but aside from that technicality spacing 
"air wound coils" from relatively small wire to large tubing is quite 
simple. There are about as many methods of making spacers as there are 
peoples imaginations and the desired appearance of the end product.

To wind a coil usually takes a form, but I've wound many from half inch 
copper tubing down to literally thousands out of 1/8" pure (pure to 5 
nines) silver  and most sizes in between strictly by hand.
So to do the winding you usually need a form somewhat smaller than the 
end result for the coil. (after winding it'll spring out in diameter and 
maybe lose a turn or two.  If you use "strips" of plastic, the coil 
and/or strip needs to be held solidly. The coil can be heated so sink 
into the plastic or glued in place.  Typically "spacers" are used with 
tubing and glued in place. (they can also have flanges that keep them in 
place). Winding over the pacers usually produces a noticeable flat spot 
between the spacers.

I've also seen flat 1/4" thick plastic sheet used with groves cut on 
each side for the coil. A "Rat Tail" file does a nice job of making the 
indentations or the sheet can be drilled and then the edges cut off. 
Some one used to sell a ready made tank coil like that.

I don't remember the article listed above, but it probably will take you 
through it step-by-step.

73 and good luck,

Roger (K8RI - ARRL Life Member)
N833R (World's oldest Debonair)

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