[time-nuts] Sun Outage
henry at pericynthion.org
Thu Oct 9 19:27:20 UTC 2014
On Thu, Oct 9, 2014 at 11:18 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> What's the beam width of the DirectTV antennas? Does it agree with the "3 or
> 4" minutes at the back-of-envelope level?
DirecTV is a Ku/Ka-band system operating with a 460mm dish antenna.
At Ka-band, the 3dB full-width of the beam is 2.4 degrees. The earth
rotates at 0.25 degrees per minute, giving approx 10 minutes for the
sun to cross the beam assuming it crosses directly through the center
of the beam.
However, a little googling suggests that in fact the DirecTV
satellite signal usually has enough margin to overcome the sun noise,
but that the C-band feed that DirecTV uses at their uplink station
to receive programs from their providers may itself suffer from solar
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