It is the first time I've heard of XC, the so-called "Crackle" on HF. The Crackle is more of a "noise" station than a "numbers" station since its content is unknown...
It is now (0746z) up on 6987 kHz. The E10 station ART on 6986 kHz is causing QRM :-) but this does not trouble me; actually it is a "double pleasure"!
This is a sound sample from 6986 kHz (the E10 ART frequency)
And this is a sample from 6987 kHz, from a bit later, after E10 QRT.
You may also try 5135 kHz, during night.