[IRCA] Primary AM contours

["Dan Strassberg" <dan.strassberg@xxxxxxx>]

US AMs' daytime primary contour is still 0.5 mV/m, although iBiquity and the
FCC have apparently generated some revised wording in the FCC rules that
suggests otherwise. Because of this wording, which I have heard about but
not seen, IBOC proponents have been insisting that the daytime primary
contour is now 5.0 mV/m--the required daytime contour over the CoL. However,
if this is so, AM owners should organize and bring suit because their
licenses have been modified not merely without their consent but without
their even being officially notified. The 25 mV/m groundwave contour no
longer has any significance, except in the third-adjacent-channel overlap
rule.

The nighttime primary contour is the NIF, which for most Class B AMs (except
for a handful of very old stations) and all Class C AMs is greater than 5
mV/m. The highest NIFs I've seen in recent applications to add night service
have been 95 and 75 mV/m (WADK and WNTK, repectively). Aside from the
aforementioned handful of legacy Class Bs, only Class A AMs are protected to
groundwave contours of less than 5 mV/m. Most Class US As are supposed
to receive nighttime protection to their 0.5 mV/m groundwave and 50%-skywave
contours. Whether any US Class A AMs actually receive such protection any
longer is an interesting question because interference from stations outside
the US has become quite severe. (And this does not even take into account
the interference from all of the US Class Bs on Class A channels that
conveniently forget to switch to night facilities at sundown)

--
Dan Strassberg, dan.strassberg@xxxxxxx
eFax 707-215-6367






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