In case you missed it, the 500 KW was in the 1930s. 250 KW of audio was
not easy to come by. Last I heard WLW was using a Harris 50 KW digital AM
transmitter. See
http://download.harris.com/app/publi...d.asp?fid=1489 . Digital here
means that the AM signal is digitally synthesized at high level. There is
no modulator.
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Harris has supplied MW AM transmitters of this design at carrier powers
up to 2 megawatts.