Richard Fry wrote:
"Radiator efficiency for Class A stations (other than in Alaska) must be
such as to produce a groundwave of at least 352 mV/m at 1 km for 1kW of
antenna input power. A 90-degree omni radiator cannot do that."

Most such antennas have long been in place. Surely they are
grandfathered until the station is modified.

Best regards, Richard Harrison, KB5WZI

Richard Harrison"
Richard Fry wrote:
"Radiator efficiency for Class A stations (other than in Alaska) must be
such as to produce a groundwave of at least 352 mV/m at 1 km for 1kW of
antenna input power. A 90-degree omni radiator cannot do that."

Most such antennas have long been in place. Surely they are
grandfathered until the station is modified.
________________

The minimum efficiency for Class A is 362mV/m as I posted, not 352mV/m as
you "quoted me" above.

As far as the 50kW / non-D / 24-hr operations are concerned, their
facilities have avoided the use of 90° radiators nearly from their start,
due to the commercial/competitive need to generate a very strong groundwave
while avoiding self interference to that groundwave at night from their own
high-angle radiation. The advantages of using greater fractional wavelength
radiators to accomplish this has long been known and confirmed by field
measurements.

RF

"Richard Fry" wrote
As far as the 50kW / non-D / 24-hr operations are concerned, their
facilities have avoided the use of 90° radiators...
___________________

The list below illustrates my statement above. This data for most of the
50kW, 24-hr stations with the same radiation pattern day and night was taken
from a secondary source linked to the FCC database, current as of October
2004 (typos, if any, excepted).

The average height of these radiators is 188.8°, not including
WFAN and KDKA.

Data Format =
Freq, Call Letters, Tower Height in Degrees, Notation
640 KFI 175.7
650 WSM 190.3
660 WFAN 155.3 (top loaded)
670 WSCR 181.5
700 WLW 189.3
710 WOR 177
720 WGN 195
750 WSB 179.3
760 WJR 194.7
770 WABC 180.3
780 WBBM 194.1
810 WGY 182.9
820 WBAP 192.1
830 WCCO 194.4
840 WHAS 201.1
850 KOA 207.8
870 WWL 182.1
880 WCBS 207.1
890 WLS 189.3
1020 KDKA 280.28 (sectionalized)
1030 WBZ 188.5
1050 WEPN 186
1060 KYW 180
1070 KNX 193.5
1100 WTAM 185.2
1120 KMOX 192.7
1140 WRVA 185
1160 KSL 193.2
1180 WHAM 177.1
1200 WOAI 193.2
1210 WPHT 186

RF

Richard Fry wrote:
"The list below illustrates my statement above."

Yes, and it proves your point that non-directional 50 KW broadcast
stations in the U.S. use tall towers in terms of wavelength.

The r-f is precious and it makes sense to make the most of it. Thank you
for the list of high-powered stations which can be heard far and wide. I
still regret the end of WLW`s 500 KW days.

Best regards, Richard Harrison, KB5WZI