What use is an F-call?

In the past I've mentioned the Grey Line. If you recall, this is a twice daily phenomenon. During dawn and dusk, and often slightly before and after, there is an enhanced level of DX propagation. That is, if you're listening while it's happening, you'll notice far-off stations you didn't hear before, clear as day, then five or ten minutes later they're gone.

Today I'm not going into the actual process that makes this happen, absorption, D and F layers and the like. The more you read about the physics of this, the more you'll get bamboozled with different and vociferous views.

Instead I want to talk about something that hadn't occurred to me until earlier in the week. Once I tell you the response is likely going to be the same as mine was: Duh!

So, propagation along, not across, along the Grey Line, is enhanced. So, the line is North-South, right? Well, yes and no. Twice a year it is, at the equinox, when the length of the day and the length of the night is the same, but otherwise, it's not North - South at all.

In fact, in my case, when I first learned about the Grey Line, I saw it pointing about North-North-East, South-South-West, perfect for communication with Japan from VK6 and if you're exceedingly lucky, communication with South America.

But the earth doesn't rotate vertically on an axis, we have Summer and Winter because the earth is tilted. That means that the Summer/Winter offset of the earth also affects the Grey Line.

The effect this has is that your Grey Line target countries change as the year progresses, from Plus 23.5 degrees to Minus 23.5 degrees and of course, also the opposite, from 203.5 down to 156.5 degrees. Thats 47 degrees of rotation across the whole year, twice.

So, as your hunger for DX entities intensifies from "anyone, anywhere" to "I gotta get Israel and Brazil", you now can start planning when that might be something that could be achieved with the Grey Line.

I'm Onno VK6FLAB