[BC] Class B/Class D AM Question

[PeterH]

On Jun 23, 2009, at 11:25 PM, Paul B. Walker, Jr. wrote:

> How could a station on 1250Khz with 900W Day and 370W Night non  
> directional
> be a Class D and not a Class B?

The only way I can imagine is if the efficiency at night is  
significantly less than 281.63 mV/m/kW at 1 km.

250 watts into a minimum conforming radiator would still be Class B.

I can see that KCST is licensed as a Class D with 0.9 kW days and  
0.37 kW nights.

The radiator is 28.80 degrees with 61.20 degrees of top loading, for  
a total of 90 degrees, right on the money.

The licensed efficiency is 300.00 mV/m/kW at 1 km, and that is also  
consistent with 90 degrees. With an ideal ground system, that could  
be about 310 mV/m/kW at 1 km.

Normally, if a station on a regional or clear channel produces less  
than 140.82 mV/m at 1 km at night, then it is Class D at night.

Such a station must still produce 281.63 mV/m/kW at 1 km days, however.

This is a case of Class B days and Class D nights, the so-called B/D,  
which the FCC lists KCST as.

But, KCST produces 182.48 mV/meter at 0.37 kW, which should make it a  
Class B, the so-called B/B.