On Sep 29, 10:06 am, John Barnard wrote:
wrote:
On Sep 25, 8:52 am, RHF wrote:
On Sep 25, 7:13 am, David wrote:

On Mon, 24 Sep 2007 21:13:43 -0700, wrote:
I suppose I can try KNX this morning, but I don't see any reason for
IBOC to cause motorboating. Granted IBOC sucks in many other ways, but
it should not have such an effect on the analog signal.
It's part of the IBOC signal. If you have selectable single sideband
listen to any HD AM station, one sideband only; you'll hear it quite
clearly. It's a warbling signal at approx. 400 Hz.
David - My Point Is - I Am Hearing This With An "HD" Radio :

THIS IS BAD NEWS FOR "HD" AM/MW RADIO LISTENERS !

I am hearing more and more of what we use to call
Automotive Engine {Ingition} Noise {at very High RPM}
with the Radi-Osophy HD-100 Radio.

THIS IS BAD NEWS FOR "HD" AM/MW RADIO BROADCASTERS !

When I first got this "HD" Radio this Noise was not as
noticeable -but- now it is the 'preponderant' sound across
the AM/MW Band except when there is a Clean and Clear
Analog AM/MW Radio Station to listen to on any given
Frequency.

-NOTE- This HD Radio "Noise" Background is so strong
that IMHO most 2nd and 3rd Generation "HD" Radios
should have a Squelch Knob to quiet-out this Noise so
that a Radio Listener only has to hear those 'local'
AM/MW Radio Stations with a Clean and Clear Signal :
Be it Analog or Digital.

I Ask Myself : What IBOC ?
All I See Is The Blinking Blue Light ! ~ RHF
In That Distant Land* Where IBOC Fears To Go :
Life Exists and Radio Listeners Live Beyond the 10mv/m Contour.
* Twain Harte, CA -USA-
.

Yes, I didn't understand you were using an IBOC radio. I have no
experience with one, other than trying to play with one at Fry's and
not getting it to work.

I notice that some of the IBOC hash does reach the analog channel,
even using a very selective filter. That is, the noise floor of the
analog signal is raised a bit. This is noticeable on very clean AM
signals.

I don't know if anyone has tried but is it possible to remove some of
the IBOC hash on analogue signals by using DSP audio processing?

JB

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.