[Elecraft] OT: Effect of Compression and ExpansionontheInductance of Toroids?

[EricJ]

I don't have your experience or background, Ron, but the L-meter is
measuring inductance indirectly and ignoring the presence of distributed
capacitance. Maybe it isn't as negligible at the frequency of the meter as
you think.

But in the end, it doesn't really matter. The real test is how a particular
toroid reacts in the circuit it was intended for. If adjusting the turns
spacing changes circuit resonance, then...it changes circuit resonance.
That's the result we would have been looking for. Hi.

Eric
KE6US
www.ke6us.com 

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ron D'Eau Claire
Sent: Monday, August 29, 2005 5:29 PM
To: w3fpr at arrl.net; va7to at rac.ca; elecraft at mailman.qth.net
Subject: RE: [Elecraft] OT: Effect of Compression and
ExpansionontheInductance of Toroids?

Okay, this is interesting so I approached an answer in my usual way.

I grabbed a loose toroidal inductor that had nicely spaced turns filling 90%
of the circumference of the core and stuck it in my L-meter. 3.1 uH. 

Scrunched all the turns tightly together. They filled about 20% of the
circumference. Inductance now 3.3 uH. The L-meter uses a low frequency
signal so capacitance shouldn't make much difference in the reading. 

So fully spaced to totally scrunched, in this case, yielded a 9% change in
inductance.

It's nice to work the numbers, but I've always tended toward a direct
experiment whenever possible.  

Back in school, I always knew where my soldering iron was but was forever
forgetting where I had put my slide rule. I haven't changed. 

(For the newer readers, a slide rule is the ancestor of the pocket
calculator. For comparison, a slide rule is to a calculator as working CW on
40 meters is to making a cell phone call.) 

Ron AC7AC


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