Hi again Mike, before I got stuck into doing proper logging I monitored CFH
on a waterfall every night since January 2000. The dive in noise occurs
earlier in summer (about 0300 or soon after) and later in winter. I
appreciate that this does not rule out a station going to a daytime power
regime, as that would change with daylight too....presumably. However what
is noticable in summer is that a lot of this noise is like distant lightning
crashes. They sound more like 'crunches', but provided the outlook is clear
of storms in the UK and to the west, the noise drops significantly about one
hour or so before dawn. Observations would suggest the main source maybe a
hour east of the shadow edge at that time.

I too have been surprised by the way the dual line fades out ....yes it does
fade out because I have seen a weak return about 30 to 45 minutes later for
about 15 mins before it goes completely. I assumed it was a trans-atlantic
source, but have not bothered to try to locate it further. I see the same
pattern as you and Dave.

The asymmetry on opposite sides of the Atlantic is  "my hypothesis",  not
any proven fact, but it does seem to fit the observations quite well.

Now one for the lower power stations, and the hand morse stations, the
improved level of ionisation in the D-layer should lead to enhanced shorter
range working signals, of the order of 700 to 1500kms, even in daytime,
because this is how we are receiving CFH in daytime. I would be interested
in any reports of new stations worked during the next few days.

Cheers de Alan G3NYK
[email protected]