I finally got off my fat ass and decided to locate the source of the
data-sounding signal blocking my HF reception. A quick tour of the
premises with my DX398 revealed that the noise was only present in the
computer room/ham shack (yeah, my luck). But unplugging the computer and
peripherals didn't help. So I turned off the VERY EXPENSIVE surge
protector that the computer plugs in to, and the noise went away. Turn
the surge protector back on, and the noise starts up again. I don't want
to shell out the $$$ for a new surge protector, so I'll just have to
turn it off when I listen/DX. But why wasn't it doing it prior to about
two months ago? Maybe I should buy another one...