Calculating the Height of a 0º Ray

WA3FET calculates the height of a 0º ray over London for Chapter 3

This is being cited in the discussion of the ELEA experiment in Chapter 3

Dec 4, 2021 at 10:43 PM

Breakall, James Kenneth <jkb1@psu.edu>

To: William DesJardins <w1zy@yahoo.com>

Hi Bill,

It is a little more complicated than I think what you were thinking maybe.  One has to take into account the height of the ionosphere and then find the distance that a completely tangential ray (0 deg take-off angle) would travel on 1 hop.  The height that most people use for the F-region is 320 km.  I called that h in my diagram attached.  If you use the radius of the earth and this height, then you will get a distance of 3954 km.  Most texts just round this off to 4000 km.  This is the maximum distance that a 1-hop ray can go. 

I ran VOACAP from Providence, RI, to London, UK.  That is a great circle distance of 5319 km.  As you can see, a 1 hop will not get there and it is a two-hop ray that would get exactly there.  That would of course be at a slightly higher angle.  With the question you asked of a tang…