RadioBanter - View Single Post - KNX 1070 exhibits severe motorboating at night

David · September 29th 07, 10:55 PM posted to rec.radio.shortwave

On Sat, 29 Sep 2007 11:35:03 -0700, wrote:

The IBOC hash shows up in two manners. One is due to the finite slope
of the analog IF. Essentially, IBOC sits in the guard band. [Of
course, the guardband is now "quaint", dating back to the days when
the FCC cared about protecting signals. ] Given how AM demod works,
this shows up as high frequency hiss. Some of the digital hash falls
into the analog channel. It sounds like noise right in the voice band,
degrading the analog signal. There is no linear solution to get rid of
this noise.

The IBOC sidebands would be completely audible on any receiver except
for the fact that the upper sideband and the lower sideband are 180
degrees out of phase with each other. Any asymmetry in the i.f.
passband (like selectable sideband reception) or in the propagated
signal (e.g selective fading) will upset the cancellation and the hash
and the warble will be heard.