Before transmitting data, the RTTY are stalling with just a carrier.
Usually, that carrier is just 0.1 kHz below a full kHz.
In that case, the carrier on 6572 would have been exactly on 6571.9 kHz
(but this one could have been anything else, of course,
it was gone whenI tried at 13:40 utc)
BTW, Ethernut, please use UTC...