Hi Dave,
Unfortunately, the wandering birdies are prolifically generated by many consumer products found in most homes. Anything using switching wall supplies could be suspect: phone chargers, computer peripherals, portable DVD players, power tool chargers, and the list goes on-and-on. The noise may be directly radiated, or it may propagate along the AC wiring of a dwelling. High density population areas such as apartments and condominiums are often saturated with HF birdies and other aggravating noise. Using a separate receive antenna can sometimes offer some relief. Loops can often be positioned to null out some types of HF interference successfully. The rising level of man-made HF noise from dubiously designed appliances certainly increases the challenge, but then again, if it was easy, then anyone could do what we do!
73,
Rob W1AEX