Three Items

Dan Strassberg
Fri Jul 16 12:31:26 EDT 2004

Not quite, again. AM stations whose licensed power is less than 250W ARE
allowed, PROVIDED that the RMS inverse-distance field at 1 km is at least
that which would be obtained by supplying 250W into an antenna of
minimum-efficiency for the station class (140.85 mV/m for Class B and D
stations). For example, look at the new night facilities for 1330 in
Campbell (Youngstown) OH. I believe the power is 215W, but thanks to its use
of relatively tall towers, the station remains a Class B because the
standard-pattern RMS exceeds 141 mV/m. This station is NOT unique in that
regard. The FCC uses the inverse-distance RMS to determine which stations
qualify as Class Bs and which qualify only as Ds. Sometimes, when
substantial nighttime coverage of the COL is impossible and the FCC refuses
to grant a waiver, a station will apply to drop from Class B  to Class D by
lowering its night power to fall just under the 141 mV/m Class B minimum.
That might be called "gaming the system."

Dan Strassberg,
eFax 707-215-6367

----- Original Message -----
From: Garrett Wollman <>
To: Peter Murray <>
Cc: <>
Sent: Friday, July 16, 2004 11:53 AM
Subject: Re: Three Items

> <<On Fri, 16 Jul 2004 10:40:43 -0400 (EDT), Peter Murray
<> said:
> > AM stations are measured by TPO, not ERP, to my recollection (the
> > is the case for FM, where omnidirectional gain is practical).
> Not quote.  AM stations are measured by "nominal power", which in most
> cases is either base power at the (singular) antenna, or power at the
> common-point for a directional array.  (That is to say, "nominal
> power" allows for transmission-line loss.)  The exception is an
> artifact of the old rules regarding AM station power levels, wherein a
> station could only be licensed for 1, 2.5, or 5 x 10**n watts.  If a
> class-III station (to use the old designation) were licensed for 5 kW
> into a minimum-efficiency radiator, and later built a new antenna that
> was 25% more efficient, the station had two choices: either apply to
> reduce nominal power to 2.5 kW (the next step down), or add a resistor
> network before the antenna to waste the extra 25% and restore the
> antenna system efficiency to its old value.  Nominal power is measured
> before any such energy-wasters.
> Today, a station would normally just file for the actual power needed to
> duplicate the old coverage with the new antenna system -- unless the
> station is licensed for either 50 kW or 250 W, the first for marketing
> reasons and the second to avoid a downgrade to class-D.
> -GAWollman

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