overhead keyhole question
The data sheet of an antenna system can be found at http://www.tcs.la/Portals/0/TCSXY.pdf. This description is taken from it:
Our XY pedestal is ideal for tracking satellites in Low-Earth Orbits (LEOS) because it completely eliminates the problem of the overhead keyhole more reliably and less expensively than a three-axis system.
I just can?t understand what is ?overhead keyhole?. Is it a term used in installation or something else?
Senmeis
Hi,
I do not know but wonder if it doesn't mean a blind spot, giving donut-shaped coverage but not right in the middle, that may (or may not) be habitual with this kind of antenna.
The following statement comes from the same vendor:
The systems’ X/Y axis configuration eliminates the keyhole (lost data) effect that occurs with other tracking antennas when satellites pass directly overhead.
It is clear what the term means, but why this issue?
Senmeis
Think of an antenna drive with 360 degree azimuth and 90 degree elevation range.
Do you mean this issue can be eliminated just because the elevation is greater than 90 degree?
Senmeis
In this document it states also:
Digital demodulation and Autotrack phasing at the controller.
I think demodulation shall be conducted in a Modem, why controller here?
Senmeis