In article ,
"amdx" wrote:

Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped I
think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK

Only two ideas from me, and they seem weak.

A half turn means the current goes in and out on separate sides. That
makes one turn of inductance perpendicular to the rest of the turns that
would skew the magnetic field.

If it is a powdered iron core, the volts per turn could be high enough
that it conducts electricity.
--
I won't see Google Groups replies because I must filter them as spam

I tried reading and understanding most of the posts, but confess not
understanding all of them.
BUT, I cannot resist inserting my "two cents" worth:

In olden days, it was quite common (but unwelcome) to have parasitic
oscillations run away in large RF amplifiers. They would start all by
themselves and quickly begin roasting tubes, coils, even adjacent conductive
surfaces, whatever got in the way. The often encountered case would be a HF
amplifier running away (self-oscillating for the unwashed) at a VHF or UHF
frequency.

One common, but mysterious result was burned parts of RF chokes in the
plate circuit. (you do remember tubes, right?) I think there were a couple
of commercial RF chokes wound on long ceramic (steatite?) cores with
assorted winding spacings on the ceramic core. Burned spots would occur in
only one or two places on the length of the winding. Caused, supposedly by a
high current node on a VHF or UHF resonant portion of the winding.

4 1/2 turns at 600khz must be an awfully low impedance circuit, but
could be right down the alley for VHF.

Brian has my vote for barking up the right tree.

Old Chief Lynn, W7LTQ

Hey OT:

I stand by my proximity effect.

The Q is equal to Rl/Xc the half turn has twice as much Xc so the Q
for that turn is half as much as the other turns because of proximity
Thus the Pd in the half turn is 4 times the Pd in the other turns.

73 OT
de n8zu



On Aug 25, 12:09*pm, "amdx" wrote:
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped I
think,
but it has been awhile. The inductor was driven hard but below saturation..
The problem; the 1/2 turn got HOT. *Four turns or five turns were ok.
*My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

* * * * * * * * * * * * * * * * Thanks, MikeK

A 12 bit insulator is 4/3 bytes a half turn is 1/X or 8 bits...

"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK