Re: Variable Capacitance and Inductance

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

Dave:

Tesla list wrote:

> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

> Hi Gary,

> Radios are tuned to crystals precisely because inductor/capacitor only
> circuits do drift.


	SOME radios are tuned by crystals.  Many are not.
	cf any book of radio design, rf design, radio history.

	With one _not_ tuned by crystals I routinely leave it
	on, volume down, turn it up, and there is the BBC on
	SW, 'just where i left it'.  With another such, even
	older, i was listening to 'Radio Australia' (Properly: ABC
	Australian Broadcasting Company  But that confuses people
	in the US, with the OTHER ABC) one day.  Next day i snapped
	it on and there they were.  (Both to a site in Eastern MA,
	USA...)

	Capacitors can and do change value, as many people have
	advised.  Formulae for all (?) these effects are known
	and routinely used.  Similarly for inductors.

	best
	dwp