[BC] Question About Class D AM Stations

[PeterH5322]

>I have a question. I know the minimum required nowadays for new AM stations
>is 250W Day and night, however some stations are Grandfathered in at lower
>power.

There were two Class C stations on regional channels which were 
grandfathered at 100 watts (0.1 kW).

But these are no longer permissible, and, indeed, one has been deleted.

The minimum RMS for a Class B is 140.82 mV/m/kW at 1 km.

This can be met with about 100 watts into a 225 degree radiator.

Any combination of transmitter power, and radiator efficiency, which can 
produce a minimum of 140.82 mV/m/kW at 1 km can be licensed as a Class B, 
and on any frequency except 1230, 1240, 1340, 1400, 1450 and 1490.

Some stations intentionally apply for a tad less than 140.82 mV/m/kW at 1 
km, so that these stations can be Class D, and, therefore, be exempt from 
COL coverage requirements.

The usual strategy is to apply for the maximum possible for days, and 
just under the minimum for nights.