Re: [amsat-bb] Beam Headings for the Birds

[Tate <73KC7ZRU73@xxxxxxxxxxxxxxxx>]

This may be an over application of KISS - but here goes:

Terrestrial great circle paths exist because the earth is a sphere (at least
close enough for this thought model)

A satellite in orbit about this earthly sphere is also moving along the surface
of another sphere - it's orbit.

Great circle still applies.

Only difference would be the relative angles dictated by connecting the
shortest possible line from a point on the surface of the smaller sphere to a
point on the larger sphere (without re-intersecting the surface of the smaller
sphere - unless you're working some of the unusual propagation we've been
hearing about).

So I'd say, yes - great circle thinking applies - mostly

Ok gurus - close enough?

73

Jon Ogden wrote:
 > 
 > OK
 > 
 > Here's a question perplexing me for some time:
 > 
 > Does the RF signal path to and from the birds follow a "Great Circle" route
 > or not?  For example. when I see a bird south of Hawaii my tracking program
 > says to point the antennas West.  This would be pretty much akin to a great
 > circle route from my location (Chicago), yet drawing on a map, west is not
 > in a straight line to the bird.
 > 
 > I understand the concept of the great circle routes for HF propagation.  But
 > a satellite is above the surface of the earth so why would the signal still
 > follow the great circle route?
 > 
 > Any comments?
 > 
 > 73,
 > 
 > Jon
 > KE9NA
 > 
 > -------------------------------------
 > Jon Ogden
 > KE9NA
 > 
 > Member:  ARRL, AMSAT, DXCC, NRA
 > 
 > http://www.qsl.net/ke9na
 > 
 > "A life lived in fear is a life half lived."
 > 
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