[RFI] unknown signal

[Van Fair]

For months I have noticed and S2 to S5 signal on 24.960 in the middle of the 24 meter amateur band. In SSb it just causes a tone but on Am it appears to have some kind of low level modulation.  Here in South Carolina it is stronger with my antenna to the north and I don't hear it at all when my beam is east or west. It could also be in the South.  It is on 24/7.  Anyone else hear it?  Any ideas on what it is. Van W4GIW