Three Items

[Garrett Wollman]

<<On Fri, 16 Jul 2004 10:40:43 -0400 (EDT), Peter Murray <pete@partnercomm.com> said:

> AM stations are measured by TPO, not ERP, to my recollection (the reverse 
> 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