It can be a pain in the ass, but you need to take a deep breath at start as Robb has said, eliminate each source of suspected noise.
Turn the radio on and unscrew the coax.
If the noise goes away, that will eliminate the radio/power supply.
His next suggestion is good, go through the breaker box, shut off one breaker at a time and see if the noise goes away.
Many things in todays home can cause noise, if you find that the noise stops with one breaker turned off, turn it back on and then go through everything that is powered by that breaker and un plug it until you find the source.
He is also correct, if you have a mobile, do you get the same noise?
There are outside sources, I often notice, Gas station pumps, Doctor`s offices,medical building`s etc can sometimes be a source of noise.
Take your time, try to pin point the source.
73
Jeff