"G=E9ry Duyck" wrote:
=

I made a good deal today!
I bought 12kg (=3D26.5 pounds) of 0.9mm (=3D 20.5awg) varnished coper w=
ire for
20 euro
(=3D$23 US).
Pretty cheap isn't it!
=

I want to wind some flat coils with it to use with my homebrew PI metal=

detector.
=

I place 2 sheets of plexiglass above each other with a round piece of
plastic
with the thickness of my wire and the inner diameter of my coil.
Then I start winding (40 turns).
=

Even if I wind very carefully twe wire keeps on moving above each other=
,
so I don't have a neat sipral :-( It's very frustrating !
=

Now I just do it with one piece of plexiglass and the round piece of pl=
astic
glued on it,
and just wind and glue it together at once.
That's working, but it takes a while before your coil is finished!
=

Is there any trick for winding sprial coils ?
I saw some pictures on the internet with homebrew spiral coils, but wit=
hout
explanation...
=

Any tips or hints would be welcome.
=

--... ...--
Gery D.

The coil does not have to be perfectly flat to have a flat spiral
characteristic. The really easy to make one is to use an
nonconductive coil form shaped like a daisy with an odd number of
petals. You pass the wire between the petals and every turn passes
through the slots the opposite way from the previous turn. This
actually produces a lower stray capacitance coil than the perfect flat
spiral.

-- =

John Popelish