Thanks for the report. I think you have found the source, but there could be other sources. The component that usually causes the interference is the power supply. The power supplies now being used are called switch mode power supplies (SMPS), or "switchers" for short. They are more efficient than the older linear power supplies but have a tendency to produce a lot of EMI unless they have the proper filters installed.
https://en.wikipedia.org/wiki/Switch...e_power_supply
If your PC is a desktop, the power supply is inside. If you have a laptop, the AC adapter is the usual source and it is sometimes possible to buy an adapter that is less noisy like MikeBear did.
Some people modify the power supply in their computer and install extra filters, but that is beyond the ability of most users.
http://ka7oei.blogspot.com/2012/12/r...racket-rf.html
http://ka7oei.blogspot.com/2014/08/c...ing-power.html
I don't know of a source of low noise power supplies for a desktop, but this one claims "Premium EMI/RFI power filtration provides low noise and ripple for stable power delivery."
http://www.newegg.com/Product/Produc...w&gclsrc=aw.ds
EMI can be radiated through the air to your antenna or conducted through the power line, or both.
If the interference is radiated through the air the cure is to increase the distance between the source and the antenna.
If the noise is conducted through the power line, sometimes using a different circuit helps. An AC line filter can be installed near the source, and one can be installed near AC operated equipment that is being affected.
http://www.repairfaq.org/REPAIR/F_CompRFI.html
from the ham radio viewpoint