Re: [amsat-bb] 2.4 gHzCordless Phones

[Bruce Bostwick <lihan@xxxxxxxxxxxxxxxxxx>]

At 9:26 PM -0600 1/19/01, laura halliday wrote:
>All the microwave ovens I've heard on 2.4 GHz produce
>a 60 Hz "rum-rum-rum" sound.
>
>The design are actually pretty slick: at DC, a cavity
>magnetron is a diode. So the tube generates the DC pulses
>it needs, all by itself...

Depending on the voltage .. the magnetron's frequency goes up in 
steps with the voltage, so if the transformer voltage is too high 
(out of spec power supply voltage, and so on) the magnetron will kick 
up to its second harmonic sometimes -- IIRC, the voltage drop across 
the magnetron will jump proportionally.  Old radar equipment used to 
have fits when the magnetrons did that, and it used to be classic 
microwave troubleshooting to look at the magnetron voltage during a 
pulse and check for the characteristic higher voltage spikes of mode 
jumping .. and I think a 2.45 GHz waveguide will pass the second 
harmonic, maybe not too efficiently but it would pass it ..

-- 
<BGB>
                  --... ...--  -.. .  -. ..... ...- -...
              Bruce Bostwick  N5VB  Austin, TX  Grid EM10DH
     ARRL / UT ARC / Austin ARC / Travis Co. ARES / W5YI Vol. Examiner
    http://ccwf.cc.utexas.edu/~lihan/  mailto:lihan@ccwf.cc.utexas.edu
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