Re: Off-Axis Primary Inductance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Steve Cook by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<steve-at-g8cyerichmond.freeserve.co.uk>
> 
> One of the early ways of making a variable inductance for use in radio
> tuning was to divide the inductance in 2 pancake type coils and then hinge
> one relative to the other, by moving one relative to the other inductance
> could be varied as far as I know it was never done commercially but I have
> seen it used in amateur built equipment from the early 1900s.

	Exactly that configuration IS illustrated in some of the early
"wireless books", including Zenneck's classic "Wireless Telegraphy. 
That configuration must have significantly greater loss than the classic
"ball variometer", but sure is a lot easier and cheaper to build.  The
stuff I have on the really big (>250 kW) stations all used the latter.

Ed