Topband: Long Daytime Propagation

[Jim Brown]

While we're talking about propagation, I'd like to understand what form 
I'm experiencing during the beginning hours of 160M contests. They start 
at 2 pm out here on the left coast, which is at least 2 1/2 hours before 
sunset, depending on which contest. Within the first year after moving 
here, I've had a dipole at 120 ft and a Tee vertical with a lot of 
radials.  I find that I can repeatably work the better stations at 
distances of 800 miles or so on the vertical, but don't get even a QRZ? 
from the dipole  (I'm 70 miles S of San Francisco, so that includes 
Seattle, Phoenix, Salt Lake City, and parts of WY, MT, NM, and CO.

Now, 120 ft is only a quarter wave on 160, so that's still a "low 
dipole," and the radiation at low angles isn't as much as from the 
vertical, but the difference seems greater than just angle.  So I'm 
wondering what form of propagation this is at this time of day? Could it 
be ordinary ground wave?

Also by 3 pm I can always hear the stronger stations from W9 and VE3, 
but can almost never work them. I understand the differences in the 
noise levels between my daytime and their darkness, and there's also the 
fact that they're all listening with NE RX antennas.  But again the 
question is, what form of propagation is this? W9 and VE3 are 2,000 
miles from me, and the path is in daylight!

73, Jim K9YC