On last Wednesday evening, I was tuning past WGN and I heard alot of
noise just above and below WGN's carrier and sidebands. I didn't notice
any interference with the station's audio, but I wasn't listening on a
wideband receiver. The noise wasn't like anything I'd heard on the AM
broadcast band before, but it did sound much like the digital noise from
DRM transmissions. I noticed the noise around 7:35 pm, Central time.
The noise was gone by 8:00pm. I haven't heard the noise since then.

WGN has recently installed some new equipment (and dropped AM stereo),
so my first guess was WGN might be testing the IBOC system. I e-mailed
WGN's engineer and he replied that the noise wasn't from WGN, and if it
was IBOC, it must have been from someone else.

So, my questions a

Does my description of the noise seem like it might be IBOC?

If so, who might have been testing on 720 kHz?

Frank Dresser