On 07/09/2011 10:16 AM, Bill Bradburry wrote:

This is not a big problem since I can not hear the hum when in flight, but I thought someone might be able to tell me how to stop it.  I have the Renesis and I am using the stock capacitor that is attached to the engine.  When I turn on the alternator, there is a slight buzzing hum that appears in the headset and the frequency goes up and down with the engine.  It is pretty obviously the alternator I think.

 

Does anyone have any suggestions?

 

Bill B

How do you have your audio system grounded, Bill. 

People make ground loops more complicated than it really is.  If you'll just keep in mind that every wire is also a very tiny resistor, I think most of the misconfigured grounds would solve themselves.  I think what I've seen a lot of is people will ground there radio at point A, and the intercom at point B.  Electrons from the charging system (or any other noisy system like strobes) have to pass through A and B to get to the battery (the ultimate source AND destination of all electrons in the system).  Because the conductor between A and B is a resistor, a small but very real voltage is created.  Because the audio system is designed to work off of very small voltage, you can hear every change in the A-B voltage.

The solution is simple.  Don't allow ANYTHING to route its electrons between the ground points of all the audio equipment.  Bring all the audio grounds to a single point and then that single point to a good ground with a single wire.  I actually made a separate circuit board to connect all the audio stuff.  Everything comes to jumpers on that one board, and there is a single ground line.  I tested my audio equipment last week with the engine going strong.  Not a single bit of noise. 

Well, at least not electrical noise.  There was LOTS of exhaust noise.  8*)