Need some cheese for that Whine?

[wb7sgl]

So I installed my 30 watt amplifier in my truck and used the accessory plug charger with my radio for a recent Net. When I started the engine, there was so much noise from the alternator that I had to shut off the engine to continue.

This bothered me for some time and I set out to identify a solution.

My vehicle is a 1987 Jeep Cherokee. I replaced the alternator last summer so I know it was good at some point.

So the noise can be from two things:
1) The alternator may have a blown diode allowing extra AC on the DC line.
2) The alternator may simply not have enough filtering to kill all of the AC.

Well, I am not one to pass up an opportunity to learn something new! After all, Hams are referred to as the "McGuyver's" of the radio business. In times of emergency, our resourcefulness helps us solve problems with minimal formal solutions.

So, I started with Google. I searched and searched for a cure to my "Alternator Noise". Finding nothing, I searched for "Alternator Whine" which yielded a greater number of relavent results. The one I followed was here.

The results were incredibly impressive. the noise is all gone, period.

Here is the circuit:


The 12Ga wire should provide 20 Amps or better, plenty to drive a good radio or in my case, an HT and an Amplifier.

Hope this helps someone! Thanks go to WB1MVX for the original writeup!

Rob