[BC] Documented harmful interference

[Barry McLarnon]

On Friday 20 January 2006 01:13, Phil Alexander wrote:
> On 19 Jan 2006 at 19:29, DANA PUOPOLO wrote:
> > Today I was in Worcester. WILD's main channel barely comes in there,
> > but their IBOC on 1080 was strong enough to put hash under WTIC 1080
> > from Hartford, a class A station running 50kW Non-D. Worcester is a
> > city of about 100,000 well within WTIC's daytime coverage contour
> > (perhaps 55 miles away as the crow flies). The hash was there all the
> > time and was about 10-12 db down from the WTIC audio. It made WTIC
> > quite tiring to listen to.
> >
> > How come an analog AM station has to protect the WTIC .10 mV/m
> > contour, while and IBOC carrier can DUMP all over it?
> >
> > Anyone??
>
> *IF* WTIC wants to make an issue of it, WILD probably would reduce their
> digital level a few dB, either voluntarily or involuntarily. It is clear
> WTIC is entitled to protection in its primary service area.
>
> However, according to 73.21(a)(1) while, "Its primary service area is
> protected from objectionable interference from other stations on the
> same and adjacent channels," "its secondary service area is protected
> from interference from other stations on the same channel." IOW, the
> primary coverage gets co-channel and adjacent channel protection while
> the secondary area gets co-channel protection only. By FCC definition
> WILD is adjacent channel interference. The fact that WILD *emits*
> directly in WTIC's channel is not recognized by that definition.

Huh?  What's "secondary" got to do with it?  Secondary coverage refers to 
nighttime skywave coverage, and is therefore irrelevant in this context.
The primary daytime coverage of a Class A station is protected to its 0.1 
mV/m contour against co-channel interference, and to its 0.5 mV/m contour 
against adjacent channel interference.  Period.

> 73.182(d) further defines, "The groundwave signal strength required to
> render primary service is 2 mV/m for communities with populations of
> 2,500 or more and 0.5 mV/m for communities with populations of less than
> 2,500.

Also not relevant in this context.  This deals with minimum levels of 
service, not interference protection per se.

> Thus, it appears WTIC would have to show objectional interference as
> defined by relative signal strengths within their 0.5 mV/m contour in
> a town having a population of less than 2,500, or within their 2.0
> contour in one more than 2,500. Based on such a showing, the FCC might
> grant relief, or depending on the next report and order, a higher
> threshold may be set. Realistically, they will probably have to show
> that WILD exceeds the NRSC-5 mask within their primary service area
> before anything is done about it.

The COL stuff should not really enter into the equation... a protected 
contour is a protected contour, no matter where it lands.  Granted, you 
may not get very far complaining about interference in an area inside that 
contour that is largely uninhabited.

The problem, of course, is that protection ratios that were designed for 
protection from analog adjacent channel stations completely fall apart 
when the hybrid IBOC system is used.  The FCC should have done due 
diligence on this point, but instead, they fell for the ruse that anything
"under the mask" is okay.  They bought the NAB/NRSC party line that
interference problems would be minimal.  Now they're backed into a
corner, from which there is no graceful escape.

Let the litigation begin!

Barry

-- 
Barry McLarnon VE3JF  Ottawa, ON