Ionospheric Radio Propagation

[ChrisSmolinski]

I am about half way through this excellent text https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph80.pdf

There's a section on Skip Distance Focusing (page 226) that describe exactly the effect I noticed when a station is going long, the sudden increase in signal strength before it does. Now I have the official name for the phenomena 

[Terry]

Interesting and a good catch. I hear in almost daily around gray line on the 40 meter DX group I listen to. It is like someone throws a switch. BTW, I went and found my hard copy of the book. The price printed on the title page was $2.75. 1965  printing. Big money for a newlywed. And still married to the same woman.
Thanks for posting. I need to re read the whole book.