Heating in 4-1/2 turn inductor

I take it that is dimensions in mm. What material? Minimum "thickness" (cross section)

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.

Brian has my vote for barking up the right tree.

Old Chief Lynn, W7LTQ

Here's the pdf on the core I think was used. The material was 3F3. I don't know the gap size, I thought we generally used the 160 gap, but I don't even see that listed. I decided it's more likely we used the

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.

d I

ikeK

Thanks, i will have to study some to be able to read that datasheet.

Q equals reactance/resistance, not resistance/reactance. Xc is capacitive reactance, not inductive reactance. The voltage across an inductor having resistance does not depend on Q alone, the "4 times" is complete nonsense.

Hey OT:

The capacitance of one winding to the next is still present. In this case a half winding.

More axactly in the 19th edition of Bill Orr's Radio Hand book page 11.28 if you care to look it up. We all know Bill Orr won't make such a glaring error. What you are looking at is RS, Not RL So Q equal to Rl/Xc it is also equal to wXc/Rs. The DF in the Xc is exactly what you state So it's still 4 times the power loss in the half turn. But every one knows DF equals 1/Q So in essence you agree with me.

Later OM de n8zu

On Sep 5, 11:57=A0am, Fred Abse wrot> On Sat, 04 Sep 2010 16:57:22 -0700, raypsi top poste

=A0 =A0(Richard Feynman)