[RFI] Ambient Noise Levels

[Kelly Johnson]

In the morning (let's say 7am local time) my "ambient noise" on 40
meters is about S0 to S1.  In the evening (let's say 10pm local time)
it is S4 to S5.  Normally, 14Mhz and up tend to behave the opposite
since the band closes at night and atmospheric noise decreases.  Is
this increase in noise at night on 40m due to atmospheric noise or due
to increased use of electronics by my neighbors at night?  The noise
actually sounds more like atmospheric noise, but I'm not sure.  Anyone
else have a theory?