Quote:
Originally Posted by Snore
First did some more testing. If you know the longitude, you can orientate the small antenna to “see” that way. This allows 5-bar coverage for longer periods. I will be putting the longitudes of the orbits in the front of my log book.
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Wellll... *grin*
The
Iridium constellation is inclined at 86.4° (Globalstar is inclined at 54°). That's the angle each of the six orbital planes of eleven active satellites crosses the equator. So you can use that number to aim a directional
antenna parallel to the orbital planes. To my knowledge the planes, 30° apart, march around the planet. The longitudes are not constants to my knowledge. Accordingly you need a dynamic model using ephemerides to adjust within the bounds of +/- 15° to point at the place on the horizon where the satellites rise, stay pointed as the
satellite pass, and be pointed where the satellites set. That's a lot of
work. Add in the fact that while scheduled maintance is performed over the poles
repairs and unscheduled
maintenance may take any given
satellite off line. In those cases the strongest signal may come from a satellite in an adjacent plane. On the basis of good system engineering
Iridium external antennas are omnidirectional in the horizontal plane with most gain on the horizon and less as elevation increases. In short, the only role for any directionality in a Iridium or
Globalstar external antenna is if you have a very fast fire control pointing system like those of KVH TV and Inmarsat antennas.