You can tell when an AM station is using HD Radio because there is broadband
noise in the ranges of carrier+10 KHz to carrier + 15 KHz, and also carrier
-10 KHz to carrier -15 KHz.  It is not actually broadband noise, but OFDM
(orthogonal frequency division multiplexing) which is a large number of
carriers, each with its own simultaneous modulation, designed to be very
noise-like.  Currently you can only hear this in the daytime, but nighttime
activity is about to begin.


Lloyd Rasmussen, Kensington, Maryland
Home:  http://lras.home.sprynet.com
Work:  http://www.loc.gov/nls
 
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Bob - KA5ETA
> Sent: Sunday, August 26, 2007 4:48 PM
> To: [log in to unmask]
> Subject: Re: Subject: Re: FCC aproves HD A M broadcasting 24 hours a day
> 

>  I have not been following the conversation very
> close so this question may have all ready been answered.  Here in Oklahoma
> City I have not heard that there is a HD radio station has of yet is there
> a
> site that is listing the HD station?  Or is there a way to tell if there
> is
> a HD station in the area?