Topband: 160 Meter Propagation

[k3bu at optimum.net]

> I got some interesting replies regarding the lack of long-haul DX
> communications this season.
> 
> Some theories are that there is little if any ducting going on. 
> The theory
> is that when Sunspot numbers are low that the ducts fill with
> extra-terrestrial radiation and block 160 meter RF from entering 
> the ducts.
> This leads me to believe that what is missing this season is the 
> ability of
> the ducts to accept 160-meter energy, for whatever reason.
> 
> This would account for the lack of few spots greater than 10 k 
> miles this year.
> 
> Something has definitely changed in the last year or two. I just 
> have no
> idea what it is! I just want to finish my 160 meter WAZ...I need 
> 3 zones,
> and most of you can guess where they are!
> 
> (((73)))
> Phil, K5PC
> 

The way I try to understand the "situation" and from my observations is this.
Earth is a ball, squashed at the poles, with the envelope of gas (atmosphere) and when ionized - ionosphere, which propagates our signals. The gas has some variations in thickness from poles to equator and also variation in ionization.
 
It appears that overall thickness of gas (atmosphere) layer decreases during low sunspots and due to the gas trying to envelope the ball, that decrease would be proportional at the poles and at the equator.  Gas is on the mercy of laws of physics and gravity and I can't see the reason why it would be squashed at the equator.  So if the atmosphere "shrinks" it would shrink proportionately around the globe. Then you apply ionizing radiation and heat from the sun and we get varying pictures of propagation properties.
 
Generally I observed lower angles during the sunspot minima and during the lower activity maxima vs. higher sunspots. I have seen that happening from 160 through 10 m.
It appears to me that best (long) propagation on 160 is happening when we are heading for the minimum of the cycle, just before it hits the bottom and then when we are getting out of it, on the upswing. We had "nice" long minimum and it wasn't too hot, so there is a hope that we will experience some improvements soon with some sunspots arriving, so hang in there. Just have low and high angle antennas ready when it happens. Then its amazing, like when I heard XZ coming through for about 2 hours and changing directions and long path.
I might watch for that rare opening over the pole.

73  Yuri, K3BU