Update 23-Oct-20: This was a bad idea. View the last picture in this post.
I have a little bit of alternator whine that comes through my headsets. It's not noticeable in flight, but it is noticeable on recordings of the intercom through my canopy cam. Interestingly, I do not hear any whine when my LEMO headsets (to which I also added a filter cap last year) are disconnected from ship's power.
So I decided to try an alternator filter (note, they are much cheaper sourced elsewhere). Nothing special about these. It's just a capacitor. It ended up reducing the whine a little, but it didn't eliminate it.
I mounted mine as shown in the following images.
I mounted mine as shown in the following images.
There's a hole on the alternator's metal shield that is just a bit larger than an AN3 bolt. Adding some washers made it viable.
I could get in there with a 1/4" ignition wrench to work the bolt.
Here it is from a view looking up.
Update 23-Oct-20: This was a bad idea. When I went to change the oil 7 months later, I found this. Turns out that the metal hood that I bolted the filter could not be recruited into the task of holding this relatively heavy filter in the punishing environment of an IO-390. I'm quite fortunate that the filter didn't completely separate from the airframe and depart the cowl in flight, doing damage to something or injuring someone. This was a very educative experience and a potent reminder to stay within the bounds of my knowledge: Don't do something like this that hasn't already been shown to be safe.
