Topband: Speaking of noises...

[Bill Tippett]

Does anyone know the source of periodic wideband buzzes that sound like
this:

buzzz..buzzz..buzzz..buzzz (i.e. 4X then pause)  buz..buz..buz (3X ~10 dB
down).

I believe this may be some sort of ionospheric sounder but I've heard this
for decades, including when I was in Colorado.  Hopefully someone knows
what's generating this.

73,  Bill  W4ZV

P.S. to K4PI re salt water.  NEC models show approx +10 dB and very low
angles for vertical polarization...no effect for horizontal.