[Elecraft] OT: Effect of Compression and Expansion ontheInductance of Toroids?

[Ron D'Eau Claire]

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