Many hams today have at least one computer in their ham shack. A newly emerging topic for discussion among hams has become computer interference.
Computers are generally noisy devices.
Turn your computer on, switch your receiver to a modestly shielded dummy load or simply disconnect the antenna, and tune across the ham spectrum hunting for anything other than silence. Make note on a pad of the frequencies and the s-meter readings of these noises. Next, turn off the computer and go back to the same frequencies looking for differences. If you are lucky, the computer noises don't move your s-meter, and when you switch back to your resonant antenna become undetectable. You might try engaging the computer into an actual process and make another check with the computer doing work.