[BC] AM daytimers

[Bailey, Scott]

Dan,
  I take it that this applies to directional stations, as well as non-d
stations. I've seen some daytime stations, with a direction daytime
antenna pattern (i.e. 1KW), then the FCC on gave them maybe 1 or 2 watts
at night on that DA pattern. You, I, and the rest of us here know that's
not going anywhere at night.
  Also, I hope I don't have this backwards with the FCC terms of Class
D's:
Nighttime Authority:  Stations that have more that 250 watts at night or
produce a field reading of 141 mv/m or more. (These are Class B's)

Nighttime Authorization: Stations with less than 250 watts at night or 
Produce a field reading less than 141 mv/m. (These are Class D's)


-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of Dan Strassberg
Sent: Wednesday, February 22, 2006 7:35 AM
To: Radiofldude at aol.com
Cc: broadcast at radiolists.net
Subject: [BC] AM daytimers

Paul: Your definition of a daytimer doesn't quite agree with the
FCC's--but
you're close. The FCC defines a station as daytimer (that is, as a Class
D
AM) if its nighttime pattern RMS is less than 140.85 mV/m @ 1 km. That's
the
equivalent of 250W into an antenna of minimum efficiency for Class B and
D
AMs (281.7 mV/m/kW @ 1 km). So stations that run 250W or the equivalent
at
night aren't Class Ds (because they are over the maximum Class D night
power) and some stations that run less than 250W at night but have
antennas
more efficient than the Class D minimum are also not Class Ds (because
they
are over the maximum Class D night RMS). Class D AMs are the only class
of
AMs whose nighttime service is considered secondary and therefore is not
protected from interference from other stations. Class D AMs are also
not
required to provide any nighttime service to their communities of
license.
Indeed the FCC does not require Class D AMs with nighttime authority to
use
that authority. That is, they can remain silent at night if they choose
to.

A few Class C AMs (AKA graveyarders) that run 250W may still be around.
The
minimum efficiency for Class C AMs is 241.5 mV/m/kW @ 1km. A 250W Class
C
could thus have an RMS of only 120.8 mV/m @ 1 km, yet the FCC would
still
not consider it a daytimer. The station would be required to stay on the
air
at night for some number of hours per week. I think Class Cs are
required to
operate at least 2/3 of the daylight hours and 1/3 of the nighttime
hours
unless their licenses specify limited-time or shared-time operation.
Years
ago, Class Cs (which at that time were known as Class IVs) were not
required
to provide a NIF (nighttime interference-free) signal to any specified
portion of their COLs but they still had to meet the minimum
operating-time
requirement. Probably the majority of those stations deliver NIF signals
to
substantially less than 80% of the COL. (Class B AMs are required to
deliver
an NIF signal to at least 80% of their COL, although waivers of this
requirement are common.) In the case of Class Cs, I think all stations
that
existed at the time of the rule change (meaning all but the newest US
Class
Cs) had whatever NIF coverage they provided grandfathered.

--
Dan Strassberg, dan.strassberg at att.net
eFax 707-215-6367








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