[Elecraft] Strange Interference

[Terry Brown]

I am operating portable in the southern Puget Sound area currently. I am picking up a strange S9 interference that is very narrow but generally slowly moving down the bands and sometimes up the bands. It occurs at any one point in time at 14.030, 14.060, 14.090 for instance, and occurs on all ham bands with the same spacing between the instances of interference. I started noticing this same pattern of interference at my home QRH in Oregon last week. I am running a KX3, KXPA100, and sometimes the PX3. It occurs with preamp on or off and with PA Mode on or off.   I am wondering if it is atmospheric natural or man made  interference or if something is wrong with my receiver in the KX3. 

I would appreciate any help I could get. 

Thanks,

Terry, N7TB