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Topband: Is There A Post Sunrise Peak?

To: <topband@contesting.com>
Subject: Topband: Is There A Post Sunrise Peak?
From: Tom Rauch" <w8ji@contesting.com (Tom Rauch)
Date: Fri, 17 Jan 2003 21:21:19 -0500
> I gather the reasoning is that my signal would be more detectable due to
> less
> QRN/QRM coming from farther east, but would there would be no actual
> enhancement
> of my signal.  Is that it?

No. At or near sunrise there is often, but not always, a level increase.

There is also a slight noise decrease with directional antennas at the
sunrise end of the path, the noise decrease being larger as the antennas are
poorer in directivity.

It is the "second peak" after sunrise that is not a real peak in absolute
signal level, at least as far as I can tell. That is more an upward rise
from an otherwise downward spiral, but the noise is often very low at that
time (assuming you are propagated noise limited).

> How does this compare with seeking a time of best path conditions between
> us?

The eastern end would probably hear you disproportionally better as daylight
approaches, because they would enjoy both a noise reduction and signal
increase. After daylight noise continues to drop at the east end, sometimes
more rapidily than the signal drops.

Of course this isn't always 100% reliable, but rather is a general trend.
This certainly includes all the propagation predictions I have ever
followed, which are about as good as a coin toss. Often times there is a big
sunset peak on the western end of the path, and it goes downhill from there
never to peak again that day. Other times the peak can just be at any time
when the path is in darkness.

Much good DX is missed by falling into the trap of only looking at sunrise!

73 Tom




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