Markus Vester wrote:

Attached is a spectrogram which was taken tonight on the resonant antenna. Between statics, you can still see the fourth sideband lobe which is centered near 74.6 kHz. The spectral gaps are on 74916.666 Hz,

 74270.833 Hz,
 73625.000 Hz,

with small and sharp central lines, presumably caused by slight inbalances or nonlinearities in the transmitter. By these criteria, if you have the choice I would recommend to operate somewhere near these gaps, but not exactly in their middle, and also preferably not exactly on integer Hz frequencies ;-)

Markus,

Dex