Re: [IRCA] Fw: [Lowfer] Growling audio on MWBC signals

[Barry McLarnon <bdm@xxxxxxxxxx>]

On Wednesday 22 December 2010 17:51:27 scott@xxxxxxxxxx wrote:
> > Something I hadn't known about Clear Channel stations, apparently they
> > all have this....
> > Steve
> 
> I don't think they all do yet...or even many of them. I've yet to see any
> gear installed for this at any of the stations I've visited.

I wonder if the source of the "growling"has been mis-identified.  16 Hz, 
after all, is pretty much below the lower limit of the human audio perception 
range.  Since the station in question (KSL) also runs IBOC, consider the 
possibility that this is actually the source of the noise.  The AM IBOC 
signal includes a pair of low frequency reference subcarriers (at +/- 182 Hz 
from the carrier) that are transmitted with a quadrature phase relationship 
so that they don't produce any audible output (in theory, at least) from an 
AM detector.  If you tune to the signal in SSB mode, however, this 
relationship becomes unbalanced, and you can hear a low-frequency rumbling 
sound along with the program audio.  Maybe this is the source of the 
"growling"?

Barry

-- 
Barry McLarnon VE3JF  Ottawa, ON
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