Putting ferrites on power cords that are very low impedance usually doesn't do much, if anything. Choking is easier where the line is already a reasonably high impedance, which generally means it's not carrying any serious current. I agree: Find the RFI source by running your rig on a battery (a pair of 6V "lantern batteries" in series are cheap and provide sufficient power to run the receiver for a long time -- you don't need to transmit!) and shut the AC MAIN breaker to your home OFF to cut off power to everything in the house and see if that makes a difference. It's a 15-second experiment. If it does drop the noise level, then you are the source! Remember "turning off" many appliances without literally killing the power to them doesn't really turn them off. Anything that has a remote control, for example, is always actually "on," it's just in "standby." But it's not OFF. Computers are the same. You can turn off power to a laptop or tablet or whatever, but it's still really standing by and the RFI created by the charger/power supply remains. Still...indoor antennas are the absolute worst for this -- by far. "Distance" is your friend when it comes to antenna location and RFI mitigation. If there's any possible way for you to relocate your antenna "completely outside," and preferably above your roof to be above all the local RFI sources, that can make an absolutely huge difference.