Enamel-insulated magnet wire easily gets knicked going around the sharp
corners of a core. Although the core isn't very ohmically conductive, a
knick at a corner is enough to affect the operation of the transformer.
I think the old Clifton Laboratories page had a little section of
measurements of transformer degradation caused by these knicks on corners?
Not accessible anymore.
One way of avoiding knicks, is to use Teflon tubing over the enamel (or
bare) wire.
But there's a better solution: Kynar wire wrap wire doesn't require the
second overtube.
I use Kynar wire-wrap wire from decades past. I think Kynar is just a type
of Teflon.
It's a PITA to strip Teflon wire ends without proper equipment. With the
wire wrap wire, every cheap wire wrap tool has a decent stripper.
Lots and lots of 30AWG Kynar is available both new and surplus. It's
commonly available in lots of nice colors to help you figure out which end
is which winding. The silver plating makes it a joy to solder to.
The 30AWG stuff is obviously too skinny for a transmitter winding but works
fine for receiver antennas. For transmitter transformers, teflon over
thicker copper wire works very nicely and is easy to wind and doesn't melt.
Tim N3QE
On Fri, Apr 28, 2017 at 9:14 AM, P H via Topband <topband@contesting.com>
wrote:
> I've noticed use of teflon tubing in a Flag family transformers.
> Apart from low losses: is there another reason to use teflon coated wires?
> Regards
> Piotr, SP2BPD
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