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From: wjc@ll-vlsi (Bill Chiarchiaro)
Newsgroups: net.ham-radio
Subject: FM & TV Broadcast Polarization
Message-ID: <1340@brl-tgr.ARPA>
Date: Wed, 8-Jan-86 11:47:01 EST
Article-I.D.: brl-tgr.1340
Posted: Wed Jan  8 11:47:01 1986
Date-Received: Fri, 10-Jan-86 06:46:38 EST
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Circular polarization gets some use in both the FM broadcast and
TV broadcast services.  Originally, both services had to use horizontal
polarization, but in the 1960's the FCC authorized FM stations to
use circular polarization.  In 1977, the FCC authorized broadcast TV sta-
tions to use right-hand circular polarization.  Furthermore, the
FCC allowed the TV stations to run the old ERP limit in both
the horizontal and vertical planes; I don't know if
the FM broadcast service received a similar ERP authorization.
I found the above information in the 1984 edition of "The Antenna
Engineering Handbook" by Jasik and Johnson (this is a great book).

By the way, ERP limits (in each plane) for TV stations are:

	Channels 2-6		100 kW
	Channels 7-13		316 kW
	Channels 14-83		  5 MW

I don't know of any stations that actually run the limits.  The most
powerful station that I know of is Channel 68 (WQTV, I believe) in
Boston at 1.3 MW ERP.

Some special TV transmitters, such as translators and boosters, have much
lower ERP limits.

Bill
N1CPK