Spring Arbs Shockers

Scott Fybush scott@fybush.com
Fri May 26 13:24:07 EDT 2006

Garrett Wollman wrote:
> <<On Fri, 26 May 2006 11:14:22 -0400 (EDT), "Stephanie Weil" <stephanie@gordsven.com> said:
>> IBOC AM's gonna be a disaster for all these tiny stations.  The clears
>> will probably be able to get away with it though.
> Glynn Walden claims that the opposite is actually true: that the noise
> floor for those stations is so high already that an additional -20 dB
> of IBOC all around won't make much difference, whereas the big
> stations on relatively clear channels will get hurt by their
> big-signal first-adjacents.  (He's very open about his goal to have
> all broadcasting completely move to digital within ten years.  IBOC
> will certainly accelerate this, but I doubt it will happen in a way
> that benefits CBS.  5-kHz AM already sounds like crap.)

A senior engineer of my acquaintance (and Garrett's), who does 
corporate-level allocations work for one of those Big Broadcasters That 
Starts With A "C", has pretty much staked his entire career on the idea 
that when it comes to AM in the modern environment, there is one factor 
- and one factor only - that matters, and that's the NIF (nighttime 
interference-free) contour, which is a factor of both the desired 
station's own signal level and of the level of incoming signal from 
other co- and adjacent-channel stations.

If you subscribe to this theory (and I do), it becomes clear that the 
addition of IBOC at night will create only an incremental rise in the 
noise floor on most of the regional and local channels. Up here in 
Rochester, the worst that happens to most of the ex-class III signals on 
1280, 1370, 1460 and so on is that they lose the very outermost edges of 
their currently-usable NIF signals.

For the class A clears, though, the theoretical NIF is 0.5 mV/m (which 
is to say, skywave reception is protected from interference to the 0.5 
mV/m contour). That's a pretty fragile signal level, and so ANY new 
interference becomes exceedingly noticeable and objectionable. (Think 
about how often and how easily the AM DXers catch stations running day 
facilities at night on the clear channels, even with fairly low power, 
when the same power at the same distance would just fade into the 
ambient noise on the regional and local channels.)

The former class II stations (now class B) on clear channels, such as 
WRKO and WEEI, will fall somewhere in the middle. They already operate 
with much higher NIFs than the class As, so the noise floor on their 
channels is higher already, but the channels tend to still be clean 
enough that there's at least some audience outside the NIF contours. 
(Hmm...Sox, WRKO, 2007, Metrowest...)

The point to take away from all of this, I think, is this: the advent of 
night IBOC, if it comes to pass, will force a lot of stations with 
optimistic owners to sit down and take a good hard look at their 
licenses. If you bought a class D license that says "Quincy" on it, then 
what you've bought is protected coverage of Quincy (and, if you're 
lucky, vicinity) during daylight hours. Anything else is gravy - and 
subject to going away without any legal recourse. The TANSTAAFL 
principle applies. If you wanted a class A signal in Boston, you'd have 
had to pay class A Boston money for it.

That, of course, is just the engineering side of it. On the programming 
side, broadcasters are very nervous right now, and some companies are 
making moves that may not be healthy for the long-term survival of the 
AM band, digital or not. It hasn't happened in Boston *yet*, but in New 
Orleans, Salt Lake City and, soon, Phoenix, Entercom and Bonneville have 
begun simulcasting the news-talk programming of their huge-signal AMs 
(we're talking gigantic sticks like KSL and WWL) on equally huge-signal 
FMs. If that doesn't send the message to listeners that AM is a 
redundant medium, offering nothing that can't be found (with better 
sound quality) on FM, I don't know what does. I have to believe that it 
lowers the overall value of the remaining decent AM facilities - but 
it's also understandable that skittish broadcasters are trying 
everything they can throw out there to stem audience erosion to all 
those other media choices.

And yet you've still got plenty of folks willing to throw millions upon 
millions of dollars out there to buy marginal (or at least second-tier) 
AM facilities, for whatever reason. Interesting times.


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