Need Some RFI Help

[bryan_herbert]

Ive always battled extremely harsh RFI in my apartment complex. I know the interference I receive from 160-175 MHz is from my laptop. But tonight I discovered the interference to my shortwave receiver is actually coming from the electrical wiring in the walls. When you attach a wall adapter it turns the adapter into an antenna slamming the signal meter and filling the speaker with noise. I unplugged two wall adapters a few minutes ago and instantly began hearing stations I could only hear if I took my portable receiver outside. Unfortunately I use the two adapters for charging my cell phone and my HT. I could probably arrange a schedule to operate them at seperate times but that seems troublesome. Is there any way to trap the noise in the wall and keep it from utilizing the power cords as an antenna?

 

[n5usr]

Actually, that issue is with the adapters themselves. Most small wall-warts now are switching power supplies, and many are very cheaply made. A poorly designed switcher can generate a TON of hash all over the place.

Short of finding a better-made supply (or an old-style one with a transformer in it), all you can do is turn them off or unplug them when you want to use the radio. Simplest way is to buy a cheap power strip to plug them in to, and just turn off the power strip when you want to do radio.

 

[davidgcet]

try wrapping the power cords thru a ferrite bead, this will cut some of it out hopefully enough to make a difference. also verify that your outlets are wired properly, if the hot/neutral are reversed you can get a ground hum. hot to brass, neutral to silver on the outlet screws.

 

[bryan_herbert]

Yeah they're not cheap adapters. If you unplug everything from the outlets, even standard wall cords, then hold a portable AM or shortwave receiver up to the wall, especially right up against the wall outlet, were talking a slammed signal meter. Its like this through out the apartment complex, if I walk up to the kitchen wall of another apartment, I get the same hash. Ill try the ferrite bead on the transformers, but ill need to find some sort of an AC filter for my power strips.