Richard Fry wrote:
"The most common radiator height for Class A non-directional AM
broadcast stations operating at 50kW day and night is 195-degrees."

I won`t challenge that as I have conducted no survey. WJR Detroit is
shown on the broadcast allocations map book as an unlimited (day and
night) 50 kilowatt Class 1 station.

Class 1 stations operate in a clear channel (this does not mean alone on
the channel) with an assigned power between 10kW and 50kW

A Class 2 station operates in a clear channel with an assigned power
between 250W and 50kW. They must operate so as to not cause interference
to the Class 1 stations. There are 29 clear channels which permit class
2 station operation.

Class 3 stations share regional channels and operate with assigned
powers between 500W and 5kW. Thyere are 41 regional channels and more
than 2000 Class 3 stations. These numbers were taken before expansion of
the AM broadcast band which has grown the totals.
Class 4 stations operate in assigned local channels with no more than
1kW day and 250W night assignments. There are 6 local channels with 150
or more Class 4 stations on each channel.

Primary service area is the statiob`s groundwave coverage. Secondary
service is uninterfered skywave coverage. Intermittent service lies
between the primary and secondary service areas.

A clear channel has one or more high-powered stations which serve wide
areas. All primary service areas and a substantial portion of their
secondary service areas are cleared of objectional interference.

A regional channel has stations not exceeding 5kW which have coverage
contours which limit the primary service interference between these
stations.

A local channel has stations not exceeding 1 kW daytime and 250 watts at
night. Primary coverage is limited by interference. Assignments are made
to limit interference.

Radio waves are radiated into a hemisphere as space below the antenna is
hidden by the surface of the earth. This results in a formula for the
field power at one mile from a perfect radiator emitting 1 kilowatt:
P = 1000 / 16266419 = 0.00006 watts/sq mtr
E = sq rt (PR)
and R=377 ohms

Volts/mtr=152 at 1 mile from a perfect infinitely short uniform
hemispherical radiator.

From a 1/4-wave vertical, it`s about 195 millivolts per mtr at 1 mile.

From a 1/2-wave vertical, it`s about 236 millivolts per mtr at 1 mile.

From a 5/8-wave vertical, it`s about 267 millivolts per mtr at 1 mile.

Volts vary as the square root of the power. So, for 50 killowatts,
multiply the 1 kilowatt values by 7.07.

The field strengths are the inverse distance or lossless values. Real
earth has losses.

Best regards, Richard Harrison, KB5WZI