Pete KE9OA wrote:
It would be good if IBOC fizzles out sooner than later. In my correspondance
with WTMJ, I did tell them that I can phone them and actually play one of my
radios............demonstrating that actual level of interference.
We as SWLs are more aware of this type of interference because the receivers
we use are sensitive enough to hear that interference in the first place.
WTMJ's sideband noise is at the 30uV level here in Waukegan Illinois, and
many of the "household" radios that you find in homes aren't going to detect
that low of a level. Exceptions are some of the better auto radios.

What the stations are going to say is that you're outside the service
area of the station being interfered with. WSM doesn't deliver a
protected-contour signal to Waukegan, so officially, you can't get WSM
there, and so officially, WSCR's lower digital sideband can't be
interfering with WSM.

(as I understand the rules, right now WSM *does* deliver a
protected-contour signal to Waukegan at night - but IBOC proponents want
to drop all protection for skywave signals. There's no way IBOC can be
authorized at night on clear channels, or on 1st or 2nd adjacents to
clear channels (like 620), if they don't.)

But it sure seems to me like AM IBOC already is - during the day -
causing interference within the protected groundwave contours of
existing stations.

A new station (WCKD) came on the air on 1490 in Lebanon, Tenn. around
the first of the year. That's about 40 miles from the WLAC-1510 tower.
On a hunch, I drove over there last weekend.

On a typical car radio (factory radio in 2002 Ford Focus) there was
noticable IBOC QRM on WCKD *within the Lebanon city limits*. Again,
this is on a typical consumer radio - not a hypersensitive DX setup.

Again, as I understand the rules, a station (like WCKD) will not be
authorized unless its city-grade signal encompasses the entire city of
license. The city-grade contour is even smaller than the
interference-protected contour - in other words, WCKD's protected
contour extends beyond the city limits.

In other words, if I understand the rules properly, at least one
"AM"-IBOC station *is* causing interference within the protected
contours of an analog station. I would be very surprised if this is the
only example. I *believe* I've heard interference in the protected
contour of WJJM, Lewisburg (also on 1490) but haven't actually driven
*into* Lewisburg to verify.

Certainly, WCKY-1530 has ceased to be a listening option until WLAC
turns off their HD around 5:00...

FM, IMHO, is much less of a problem. Still, I think many listeners
(especially in further out suburbs, like Waukegan, and outlying cities
like Clarksville) will be surprised to learn they can't officially get
their favorite stations. (the battle between the sidebands of co-owned
96.9 Zion and 97.1 Chicago will be interesting...)

I expect to lose my only adult-alternative and my only jazz choices if
FM-IBOC is fully deployed.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Ham stuff for sale:
http://www.w9wi.com/articles/4sale.htm