"Gregg" wrote in message
...
On Dec 19, 6:17 am, dave wrote:
Gregg wrote:

I knew about the period before and after sunrise - but I hadn't heard
of that term
"Critical Hours" before.

It's usually to protect a station to the East.

Didn't know that either David. Can you tell me why specifically only
stations to the east? :-)

I would think this would be because of gray line skip. Points east will have
already begun receiving skip by the time a station considerably to the west
will have seen sunset.