Tim N3QE wrote:
And I think clear channel stations do not cut back power at night... do
clear channel stations actually still exist?
There are about 116 AM broadcast stations in the U.S. using 50 kW
transmitter power during the day. Some of them reduce power at night,
however KFMB (760 kHz) San Diego operates with 5 kW non-directional days,
and 50 kW directional at night.
Some of these 116 stations are directional day and night, and some of those
have different patterns for day and night.
The directional patterns used by some of these 116 stations may have an ERP
of around 500 kW at the center of their major lobe.
The stations using 50 kW non-directional day and night are:
KFI 640 kHz Los Angeles
WSM 650 Memphis
WFAN 660 NYC
WSCR 670 Chicago
KNBR 680 San Francisco
WLW 700 Cincinnati
WGN 720 Chicago
WSB 750 Atlanta
WJR 760 Detroit
WABC 770 NYC
WBBM 780 Chicago
WGY 810 Schenectady
WBAP 820 Ft. Worth
WCCO 830 Minneapolis
WHAS 840 Louisville
KOA 850 Denver
WCBS 880 NYC
WLS 890 Chicago
KDKA 1020 Pittsburgh
WHO 1040 Des Moines
KNX 1070 Los Angeles
WTAM 1100 Cleveland
KMOX 1120 St. Louis
KSL 1160 Salt Lake City
WHAM 1180 Rochester
WOAI 1200 San Antonio
WPHT 1210 Philadelphia
WBZ 1030 Boston and WWL 870 New Orleans use 50 kW day and night, but with
directional arrays to favor radiation over land areas.
A groundwave field intensity of 2.5 V/m or more can be present at a radius
of 1 km from the stations in the above list. That can rise to more than 7
V/m in the main lobe of a directional station with 500 kW ERP.
The original concept of a clear channel meaning that only one 50 kW, 24/7,
non-directional station was authorized on that frequency at night is gone.
The FCC has allowed nighttime service on all of them by stations located far
enough away from those on the list above when using fairly low power (some
less than 1 kW), and usually, directional arrays.
The stations listed above are given protection to their nighttime
(secondary) service areas for interference to their 0.5 mV/m-50% skywave
contour from stations on the same channels.
RF
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Topband reflector - topband@contesting.com
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