Page "government" Paragraph 620

As mentioned, the primary allocation objective to be followed in the allocation of stations on clear channels is the provision of widespread service, free from destructive interference.

During nighttime hours, because of the intense skywave propagation then prevailing, no large number of stations can be permitted to operate on one of these channels, if the wide area service for which these frequencies are assigned is to be rendered satisfactorily by the dominant stations which must be relied upon to render it.

Therefore, under our longstanding allocation rules, on some of these channels no station other than the dominant ( class 1 ) -- A ) station is permitted to operate at night, so that the 1, -- A station can render service, interference free, wherever it can be received.

On the remainder of the clear channels, the dominant ( class 1 ) -- B stations are protected as described above, and the relatively small number of secondary ( class 2 ) ) stations permitted to operate on these channels at night are required to operate directionally and/or with reduced power so as to protect the class 1, stations.

In the daytime, on the other hand, since skywave transmission is relatively inefficient, it is possible to assign a substantially larger number of stations on these channels.

Additional class 2, assignments for daytime operation can be made without causing destructive interference to the class 1, stations or to each other, and by their operation provide additional service on these channels and additional local outlets for a large number of communities.

Such additional daytime class 2, assignments are appropriate if optimum use is to be made of these frequencies, and the Commission has over the years made a large number of them.

Similarly, on the regional channels many class 3, stations have been assigned either to operate daytime only or to operate nighttime with directional antennas and/or lower power.

9.