[sci.electronics] Microwave Leakage Tester

ren@virga.rap.ucar.edu (Ren Tescher) (03/20/91)

	About 6 years ago Modern Electronics had an article on how to 
build your own microwave leakage detector, I built several and compared them 
to the microwave tester we had at work.  The LED would light up within the
'yellow' range of the most sensitive scale, but it differed between individual
units as to where on the yellow scale.

Here is the bad ASCII schematic,

                 Schottky Barrier Diode
---------------------*--|<---*-----------------
                     |       |
                     *-->|---*                 
                 Plain Ol' Red LED

Solder the diodes in reverse parallel with the LEDs leads
as short and close to the Schottky body as possible (without burning
either up!).  Leave the Schottky's leads intact and straight.  These
become a quarter-wave antenna at the microwave frequency (usually 1250 MHz).
I then glued the unit about 1 and a half inches from the end of a 
Popsicle(TM) stick with the antenna perpendicular to the length.
The diodes are available at Radio Shack (and the Popsicle at Seven-Eleven(TM).

To Use (FOR EXTERNAL USE ONLY!):
	Place one cup of water in a Pyrex container inside the uwave and
run it two minutes at full power.  While it is running, hold the tester
perpendicular to the door seals and whatever and run it along the seals.
If the LED lights or just flickers you've found a leak.  You may notice
that the window doesn't leak anything that's because the holes in the
window mesh appear as a reflector at uwave freqs.  The older Amanas
with the heavy door seldom leaked.  On some of the other makes of
ovens I found that leakage could be stopped by adjusting the hinges,
or if it leaked out one corner of the door, gently twisting that
corner inward would clean up the leak.  Food particles (yecch!) built-up
along the seals could also cause leakage (Wipe it off!).  Of course
after cleaning and adjusting, test it again to make sure you haven't made 
things worse.

Disclaimer: if the tester does light, get the microwave oven tested and
repaired professionally.
Notice: Neither Modern Electronics, Radio Shack, Seven-Eleven, Pyrex,
Amana or Popsicle corporations hold any responsibility in this post,
neither does my employer, and he _knows_ I'm not a responsible entity.
So there!