| OoH. Its the oldest issue in the book. Dissimilar metals - the classic
| is a brass throttle arm and a steel pushrod - make a tiny battery, and
| as they rub together you get micro sparks.
That's not the way I understand it, or at least that's not the entire
story. Well, sure, dissimilar metals can create a voltage, but the
effect that causes metal rubbed on metal to create RF noise is
somewhat different or at least there's more to it. For example, two
similar metals rubbing on each other will cause the same effect -- you
don't need dissimilar metals.
As I understand it, the effect is caused by a non-linear interaction
between the two pieces of metal, which causes it to re-reradiate the
RF signals it receives (including the one created by your TX, but also
signals from FM radio stations, TV stations, cell phones, etc.) at
different frequencies (the frequency change is caused by the
If the two pieces of metal are connected somewhere else (like a single
wire soldered to both pieces) then they won't make this noise, even if
they're rubbing against each other.
| Get an AM radio, tune it to a weak station and try it. You will hear all
| sorts of stuff.
That much is true. It makes a lot of noise.
To see it on your plane, just remove your prop (if it's an electric --
you don't want it roaring to life) and turn your TX and RX on and then
go near your plane and rub two pieces of metal together -- two metal
pushrods works very nicely. If you have a PPM (not PPM/DSP or PCM)
RX, you'll generally see your servos chatter.
Doug McLaren, email@example.com
Oh, spiteful one! Tell me who to spite and they shall be spoten.
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