Low angles

I often write about the benefits of low angles on this blog in relation to getting signals to great distances, delaying the first skip off the ionosphere for as far as possible.

In the other of my lifelong interests, astronomy, one often uses hand dimensions as convenient, if somewhat approximate indicators of angular size.

So, in a quieter moment yesterday, I held out my little finger at arm's length, zoomed the phone camera until a ship on the horizon's image matched its size as seen by the eye, and took a photo. Obviously, the image quality is not spectacular, but it's good enough.

 

This provides a fairly good, visual indication of what one degree looks like on the sky.  The lines I've drawn are: yellow - 1 degree span; orange = 0.5 degrees, blue = 0.25 degrees, red = 0.125 degrees.  The apparent size of the Moon and Sun are much the same - about half a degree - and is represented as a circle to the right of the image.

I think this helps get a mental picture of how antennas over near-perfect ground like the sea can really get signals out at extremely low angles.  Even at 1/8 of a degree, there's still clear access to lower elevations, where the direct and reflected radiation combine with minimal phase difference.