K6SE said:
>I've never noticed a post sunrise peak nor any sunset peak, post or
>otherwise, but I certainly have experienced sunrise peaks and can confirm
>that they exist.
>
>Perhaps the reason that a sunrise peak sometimes enhances signals only
>slightly is that it is not really a peak at all, but a drop in ambient
>noise level at one's sunrise time.
>I have always used low-angle vertical polarization, but those with
>high-angle horizontal antennas may have different observations.
That is the answer for sure. I was astonished to see some responses
reporting no post-SR peak. Back in the good old days of summer 95 when we
chatted daily with VK/ZL there was a long peak on 65 days out of 92 from mid
May to mid August lasting from 60 minutes or more before SR to 10 to 30
minutes after, usually with a significant dip at around SR. I guess you
could call it two peaks, a long peak pre-SR and a short one post-SR.
Although it is certainly true the noise went down, it was also true the
signal went up. The dip at SR was typically 2 or 3 S-points.
In 1994 the post-SR peak was often about an hour long. In 1993 from a few
minutes to about 30 minutes and only about 50% of the days.
This summary is from the log entries for a few thousand VK/ZL QSOs, all at
VE7 early morning, all high angle, the mountain not being transparent.
Ten years or so ago NM7M produced a little BASIC program that predicted the
increase in vertical arrival angle at sunrise. This gladdened my heart, as I
live in a valley with the 'horizon' towards VK that is 23° or more above
horizontal. Most of the time I used the fullwave horizontal loop, switching
to the vertically polarized half-diamond only if the signal was fading on
the loop. For a while I fed the two antennas in parallel and the signal
seldom faded.
Bob VE7BS
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