Topband: heavy seas

[Carl K9LA]

Nick VE7DXR said,

 > If there is anything in the literature about heavy seas
 > affecting radio propagation (as opposed to radar returns),
 > I would like to hear more about it.

The only literature I've found is an IEEE Ant and Prop paper in the 
January 1965 issue. It was a study of non-great circle paths on 12MHz, 
18MHz, and 30MHz. The researchers set up a 500w transmitter on KH6 with 
a slowly rotating Yagi. They set up receivers at Okinawa, Adak (KL7) and 
Palo Alto (CA) with faster rotating Yagis. By correlating the 
orientation of the receive Yagi to the transmit Yagi when signals were 
heard, they showed where the general area of scatter was for non-great 
circle paths. Many of the scatter areas were in the Pacific Ocean away 
from any land or the equatorial ionosphere (with its gradients). Thus 
they concluded that sea scatter played an important role in non-great 
circle paths on these frequencies. It would have been interesting to 
correlate sea state (wave height, period, etc) with these results, but 
I'm not sure that kind of data was readily available back in 1965.

I suppose one could extrapolate these results to our lower frequencies. 
I guess proportionally bigger waves would be needed, so you really have 
to be careful about blindly assuming this without any correlation with 
the sea state.

Carl K9LA