This entry is a catch-up for work spread over several days. The alternator whine in the headsets on the long flights to Michigan and return proved annoying enough to motivate me to try to improve the situation. I did some trouble shooting to :
Prove the noise is from the alternator - not ignition Determine that the noise is from the G496/Music input to the intercom Narrow that down to the G496 cable, NOT the music input. Try using a different ground loop isolator - no change.
Then decided to attack the noise on two fronts:
Reduce capacitive transfer by rerouting wiring in the avionics bay, and try to kill the ripple right near the source, in the engine compartment.
I isolated the battery and alternator wires in the bay and rerouted them out of the big bundle that comes through the firewall. I also pulled the G496 audio cable from the bundle and tied up the excess in a different location.
I rerouted the power wires forward of the firewall as well, and temporarily installed a 4700MF electrolytic capacitor across the regulator output. (Checked with Joe at Van's first.) Also installed a 50MF tantalum capacitor in parallel, since my research says tantalum is better for conducting higher frequency noise. This was futile, however, since I installed the polarity wrong and it popped when power was applied.
My BFR ride with Graham seemed to show quite a bit of improvement.
More testing required. Need to:
Order and replace two connectors that now will not snap together firmly. Remove capacitor to see if it really made a difference. If it did, improve mounting. Order and try a larger capacitor.