Topband: strange conditions

Tom Rauch w8ji at
Fri Feb 24 09:00:58 EST 2006

> Looking at 3B9C logs, we can see many situations where
> stations in large regions where unable to contact us while
> stations further away had extremely strong signals.  On
> memorable night with outstanding signals from the USA, not
> single station from New England was logged (New England
> being the closest part of the USA to 3B9C).  The structure
> of the E-F duct on that night simply did not allow signals
> from New England to propagate well.  If we imagine a large
> region of thunderstorms in that area, all that QRN would
> have been similarly restricted in propagating back toward

>From 3B9 roughly:

Florida 285deg  10100 miles, path straight over middle
Africa, highest path lat 28N
Vermont  313 deg 9200 miles, path over Spain, highest lat
Great Lakes 320deg  10000 miles, path over northern Spain
and VO1, highest lat 53N
W6/7    0deg 11500 miles, path over north pole, highest lat

Looks like the largest change is in latitude of the path and
direction of the path,  not distance.

When you were working the USA with good signals, where were
they from? Nothing in what you said indicates signals
skipping over an area unless you were working signals that
follow the same *path*. The distance appears to be the
smallest variation, the direction appears to be the major
change. It is documented in published world background noise
levels the quietest regions are the northern and southern
latitudes at their winter. The consistently noisy areas are
the tropics. Anyone with large directional arrays can see
this effect routinely.

We'd also have to look back at world lightning maps for the
hours when this is observed, and compare it to signal
paths....not just distances.

This is a complicated soup of things happening.

73 Tom

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