Frank Dresser wrote:

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

WOR 710 has tested IBOC and has made a mess before all the way up to 750
(and below 710), per reports. So possibly them.