On Aug 10, 10:40 am, raypsi wrote:
All I ever see for Pi coils is cylindrically wound single layer. I
remember when I built my first 6146A output cw transmitter back 40 yrs
ago, I used a B&W pre made coil for the Pi.

Depending on the Q and plate resistance you see coils for multi band
use up to 33 uh, in transmitters.

The only place I see pancake coils used is in Tesla coils, one of
which I built with a pre made 18" tall secondary coil. I wound my own
primary pancake coil.

Done right a pancake coil takes up alot less room than a cylindrically
wound coil.

A six inch diameter pancake coil can have the same inductance as a
three inch diameter by six inch long coil with the same size wire.

Anybody know why I shouldn't use a pancake coil in my final? I just
bought a 4-1000A. from ebay.

73
n8zu

Well we all know what an roller inductor is?
Here is a pix of one: http://www.palstar.com/ri20.php

So here is a link to a java program to calculate a
flat spiral pancake coil:
http://www.classictesla.com/java/calculat.html

I might have confused people with pi wound coils I'ma
not talking about pi wound coils such as the 3 pi
coil found he
http://www.oselectronics.com/ose_p91.htm

I want to use a flat spiral wound coil to replace a roller inductor.
Like the one in the above mentioned roller inductor link.
Any pro's and con's on this topic?