[RFI] 4 khz spaced birdies

[pfizenmayer]

About twp weeks ago a group of 4 khz spaced birdies showed up on 160 , 80 
and 40 (not harmonically related ) For instance on 160 
1827.970,1823.970,1819.970, 1815.970 ,1811.970   - clean as a whistle and 
stable -  tonite 80 starts at 3495.93 and  stops at about 3573.93 hard to 
tell in QRN.
.
Strangely 3510.93 and 3563.93 are inaudible if they are there , 40 starts at 
7023.85 and stops at 7047.85

Anybody have ideas what this stuff might be coming from ? I cannot detect it 
in my house with my portable rx probing around.

40 M  has very deep nulls off end of my 40 m rotary dipole

Hank K7HP