On Tue, 9 May 2006 15:29:56 +0100, Dave Doubleyew~ waifs.strays@org
wrote in :

"Dr Ivan D. Reid" wrote in message
...
On 9 May 2006 04:10:38 -0700, Norbet
wrote in . com:

Could a small paint chip affect the safe operation of a microwave oven?

No. The paint is only a cosmetic covering over the metal cavity
of the microwave oven. There should be no risk of sparking as the cavity
walls are nulls in the standing-wave pattern. The only place you should
normally be concerned with leakage of a microwave is at the door seal --
assuming no-one has been silly enough to interfere with the magnetron
feeding the cavity. Dirt on the seal or damage could allow leakage but
given that the wavelength is about (3x10^10/2.45x10^9)=12.2 cm, you need
a fairly large gap to get any significant leakage -- consider the size of
the holes in the door-screen which allow you to see into the oven but do
not
let any microwaves escape.

Huuummm, interesting, Ivan; is it possible to pad the cavity out so altering
its resonant frequency, and furthermore is it also possible to give some
idea what kind of modulation transformer would be needed so that one could
use the oven as a source on 23 cms for EME? ;-}

Well, you're starting to get beyond my area of expertise. As a
licenced ham you're probably better equipped to judge (I was just 2nd
operator on VK0KC in 1980...) I'm not sure it's necessarily a
_resonant_ cavity, but by definition the nulls had better be at the
walls. I assume it's something else that sets the actual 2.45 GHz
operating frequency -- I've had much more experience with thyratrons
than magnetrons. :-0!

Dave Doubleyew. ( G3F**.)

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. ] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".