Re: [IRCA] Missing IBOC signals

[Scott Fybush <scott@xxxxxxxxxx>]

k4ape wrote:
> Starting on 14 September 2007, the IBOC signal from WTAM was
> destroying any possiblity of hearing anything on 1090 or WBT-1110.
> 
> At 2050 EWT, I am NOT hearing ANY IBOC from WTAM or from WBT. It may
> be only conditions, however WTAM is in very strong at the moment.
> 
> As I write, The IBOC signal from KMOX-1120 disappered. I can only
> hope they have woke up and turned it off.

I have no inside knowledge about any of this (though I'm hoping to pick 
some up next week at the NAB Radio Show in Charlotte), but I have reason 
to suspect that there's a considerable amount of coordinated testing 
going on amongst the 50 kW clears and their neighbors.

The FCC may have taken AM HD off "experimental" status, but the fact of 
the matter, from the station side of things, is that this *is* still 
very much an experimental technology, with all that that implies: 
signals popping on and off the air at varied times, and so on.

Other factors that may enter into play: if an AM station with IBOC needs 
to switch to its backup transmitter for whatever reason (maintenance, 
main transmitter failure, what have you), the odds are pretty good that 
there won't be HD for as long as the backup transmitter's on the air. 
I've yet to see any AM HD installation that's backed up in any way. 
(And, yes, there are at least a handful of FMs, mostly in major markets, 
that now have backups for their HDs.)

The point is this - at least for the time being, there's every reason to 
expect we'll hear some signals popping on and off in digital, and no 
reason (yet) to think that any particular IBOC silence implies that the 
station in question has dumped digital for good.

And, as Willis correctly notes, "it may be only conditions." On one of 
the broadcast engineering lists I'm on, an engineer from NYC noted that 
he hadn't heard hash from my local WHAM for a couple of nights, 
speculating it had turned off the digital. Not so - I check it every 
night, and it's been on every time I've checked. The propagation gods 
are easily amused, it would seem...

s
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