How many daytime only stations are left?

[Dan.Strassberg]

As I understand it, the 750 km limit no longer applies, although it probably
did apply to WILD some years ago. I don't know the year (much less the exact
date) when the FCC changed the formulas used for calculating the distance to
AM skywave contours, but if you look at any application for a facilities
change or new facility for a US AM on a US Class A channel, you will quickly
realize that, even for stations such as WBZ, WWL, or ex-IBs such as WBAL and
a couple of dozen others, the 0.5 mV/m 50%-skywave contours no longer appear
to extend 750 miles. The Chicago ex-IAs are good examples. Their 50%-skywave
coverage to the east-northeast now barely encompasses Buffalo NY--a distance
of only about 500 miles from Chicago.

In WBZ's case, a directional Class D AM 1030 (WNVR Vernon Hills, IL) now
exists about 40 miles west of Chicago, 894 miles west of WBZ. At night,
WNVR runs 210W into five towers. Every "new" Class B on a Class A channel
that I've looked at is sited no closer than about 200 miles from the
co-channel Class A's 0.5 mV/m 50% skywave contour. In that ~200 miles, the
Class B's 10%-skywave signal has to drop down to 0.025 mV/m to protect the
Class A. For sure, the Class B can't send much of an ID field in the
direction of the Class A and get down to a 10% skywave of 0.025 mV/m in 200
miles. So, is Class D WNVR protecting WBZ's 0.5 mV/m 50%-skywave contour or
is it protecting a circle with a 750-mile radius from WBZ? I don't know; if
you do know, please share your info. Thanks.

-----
Dan Strassberg (dan.strassberg@att.net)
eFax 1-707-215-6367

----- Original Message ----- 
From: "Garrett Wollman" <wollman@bimajority.org>
To: "Dan.Strassberg" <dan.strassberg@att.net>
Cc: <boston-radio-interest@lists.bostonradio.org>
Sent: Thursday, January 10, 2013 11:51 AM
Subject: Re: How many daytime only stations are left?


> <<On Thu, 10 Jan 2013 10:54:37 -0500, "Dan.Strassberg"
> <dan.strassberg@att.net> said:
>
>> The reason that nighttime operation of WILD cannot fall within FCC rules
>> is
>> that, as a Class A AM, WBAL's nighttime skywave service is protected down
>> to
>> the Baltimore station's 0.5 mV/m 50%-skywave contour.
>
> You forgot about the 750 km limit....
>
> -GAWollman
>