The AM Forum

 I have some DC fan noise whirring in my receiver. If I strap a small ceramic cap across the fan will that help eliminate it? The T/R switching is done in the transmitter so that's where it's picking it up. I haven't torn the transmitter apart yet but I'm assuming all the fans are strapped to the same bus. Ferrite? Suggestions before I tear into it and risk hosing something up. I'm good at that.

 Could it be the inadequate ground situation? Keep in mind I'm on the third floor and the only ground I have is through the AC wall socket, I can't run a ground down to earth.

 I never noticed the noise before. because I was using 2 antennas. A random wire wrapped around a curtain rod on the receiver, and the micro-dipole on the transmitter. Perhaps it's because the noise level has dropped here. It's not too loud, or too strong that it covers an adequate signal, but I know it's there and it drives me nuts. When the band is quiet I hear it.

I have found an "alternator whine eliminator" kit useful for those problems sometimes. It's just a choke with the fan on one side and an electrolytic bypassed by a 0.01uF ceramic on the other side. Hookup like the fan is the offending automotive alternator. Depending on the spectrum of noise, you may have to play with caps on either side of the coil, but the coil will usually get rid of most of it.