In a message dated 03/02/97 16:51:27, you write:
>Check to see if the p-leads--the ones from the ignition units to the
>"mag" switch--are shielded. If not, shield 'em. Keep all your audio
>leads as far away from that switch as you can.
A bit old this thread, but I was suspicious of this answer because these
leads are open circuit when the engine is running. The only current that can
flow in them is charging the capacitance of the wire to ground, which is
virtually zero (might go up a bit to "negligible" if you shield them !). But
Rotax quite clearly say they must be shielded. Only a layout diagram was
forthcoming (p128, Rotax 912 maintenance manual) which doesn't identify the
components inside. But after all, this is transistorised ignition, so the
leads are control lines to bias the units off when grounded. When running,
the only reason for shielding them could be the possibility of undesirable
inputs, rather than outputs. So the shielding will not help an audio problem
but could stop a high power transmitter stopping your engine !
Roger at the factory confirms this actually happened not long ago. Makes one
wonder how many more things are waiting to get us. Perhaps the air is really
strictly for the birds.
Graham C.
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