This MP3 gives you the reason I do not really enjoy the 10m contest. Thanks to Russian or Chinese (or both) illegal taxi radios, the 10m band is full of this noise every time there is propagation to these areas – which is every time the band is open to Europe.
It is difficult enough to work an undisciplined EU pileup – but even harder when most callers are 559 and the noise is over S9.
This is not local noise – in the morning, I can run NA on a perfectly quiet band, and it is a pleasure to do so.
10M noise: