"Paul Probert" wrote in message
news
On 02/23/2011 06:43 PM, Joel Koltner wrote:

1) The really big 450kHz IF transformers you see in tube sets... why did
they wind the coils in the form of "pancakes" rather than "the usual
way"?
They do this to try to keep the self-resonance of the winding up above the
operating frequency. By spreading the winding out into series connected
pancakes the stray capacitances have a harder time shunting large
inductances. You see this kind of construction on RF chokes too.

Ah, clever!

One I was looking at the other day has some fancy weaving involved as well; it
must have been quite an interesting machine that made them.

Poking around You Tube some I see that winding single-layer (no fancy waving)
coils is quite doable at home (the Tesla coil guys are quite into it). It's
pretty slick: http://www.youtube.com/watch?v=N3N-tw6OEXw .

Thanks for the help,
---Joel