RE: Variable Capacitance and Inductance

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

Tuned circuits do drift because temperature changes affect the physical
dimensions and dielectric properties of the L's and C's. This is widely
known and not due to any mysterious new laws of physics.  But properly
constructed components can minimize these variations.  Placing components
in a temperature-controlled oven makes them immune to external temperature
variations, and altitude, time, latitude, etc. are no more relevant than
football scores.

Yes, modern radios employ crystal-controlled PLL circuits in their front
ends, but there are L's and C's elsewhere that would create problems if
their values shifted.  Imagine the dismay the Apollo crew would have felt
if they had to retune their transmitter tank circuits every 100 feet
between here and the moon.

Gary Lau 



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.

Dave

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, May 22, 2002 11:22 PM
To: tesla-at-pupman-dot-com
Subject: RE: Variable Capacitance and Inductance


Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>

If capacitance and inductance were _inherently_ affected by date, time,
altitude, longitude, and latitude, a radio tuned to a station would be
observed to drift as these parameters vary.  In practice it does not. Q.E.D.

Gary Lau
MA, USA

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

>If you have seen formulas that require the date, time, altitude, longitude
>and latitude to be input, then you will see Tesla's suggested formulas.  I
>haven't seen them.  But if there is any truth to these factors, I predict
>somebody will eventually write new formulas.
>
>Dave