"amdx" wrote in message
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"Richard Clark" wrote in message
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On Mon, 30 Apr 2007 06:37:10 -0500, "amdx" wrote:

Are you exploring an intellectual curiosity or trying to
remedy a defect in application?

No, I just have experienced the effect that Bill ask about and
gave my own pet theory about why it happens.
Now I'm looking for a little confirmation or where I went wrong.

Hi Mike,

Well, that is fine and good, but neither of you have given us any real
data, and certainly no Q values to judge if what you both experienced
was within the range of "normal" or out in left field. RF
measurements are difficult to do to any particularly fine accuracy,
and what was observed may have been simple variation due to the
measurer's proximity (offering just one of many things that can go
wrong).

Yes, RF measurements are difficult to do to any particularly fine
accuracy.
And I claim no great knowledge of how to minimize errors or even how to
recognize where they come from.


Loss still remains the province of resistance.

Richard, That's like saying rain has water in it. No matter how many
times
you say it,
I'm still going to agree with you.

Then this diverges from Bill's premise of Capacitance being the source
of loss and you and he are separable at this point of your common
experience.

Your best argument is that Capacitance exacerbates loss.

I would rephrase that as "interwinding capacitance exacerbates loss".

And with that, you have summed up my argument perfectly.

You have helped reduce my argument to 4 words.

Now, do you agree that interwinding capacitance will reduce Q?
(yes, I know it's the province of resistance)

Give me some metrics to show it is not skin effect.

The issue at hand is your (both you and Bill, or either of you
separately) loops keep changing to fit to the loss rather than to the
application. It makes for a rather strained progression of design as
loops are added, proximity becomes a greater issue, as coil length
collapses, insulation is added, and as frequency shifts to follow
these changes. It is as though a good 10M loop is evolving to operate
poorly there or, worse, in the 160M band where its resonance has
finally come to rest through optimizing for loss.

My experience is limited to winding small inductors rather than
loop antennas.

I can imagine there being enough turn-to-turn capacitance to induce
large currents, but so many correlating factors would have to ride
along with this that they could easily eclipse that contribution of
loss. In other words, it seems the goal of your argument is to raise
that capacitance, which by ordinary means has you drawing the loops
together (insulated or not). This compounds the skin effect and for a
constant frequency demands a lower inductance. The lower inductance,
in turn, then demands a smaller coil which forces a lower Radiation
resistance. A smaller coil (to again follow the demand for more
Capacitance) drives closer loops.

It seems like this is in an infinite regress.

I don't understand why you think we want more interwinding capacitance,
We want less.
I will agree that the mechanics involved in trying to reduce interwinding
capacitance
will probably reduce proximity effects and so to seperate out any affect
from the
reduces interwinding capacitance would be difficult.
I need to go,
Later, thanks Richard


Ok, I'm back.
Richard, I was starting to lean towards proximity effect possibly causing
all of the affect we have been discussing, so I did some Googling. I kept
find the
same line " increased capacitance lowers Q" But, I think you agree that as
I said
above most efforts to reduce capacitance will also reduce proximity effect.
I ran across W8JI's page, he's usually pretty exacting in his wording, and
he says,

"Capacitance across any inductor carrying time-varying current increases
circulating
currents in the inductor, increasing loss while simultaneously reducing
system bandwidth."

snip "Anything that increases capacitance will reduce component Q"

He never mentions the correlation between interwinding capacitance and
proximity effect

These line were taken from;
http://www.w8ji.com/loading_inductors.htm

What do you think?
Mike