[time-nuts] Sun Outage
W4wj at aol.com
W4wj at aol.com
Thu Oct 9 20:10:15 EDT 2014
Not all satellite TV antennas are parabolic. A typical C-Band antenna is
parabolic and aligned for one satellite. But, that could change if the
feed was modified to receive multi-satellites, while the shape of the
reflector remained parabolic. Or the antenna could be an off-center
fed elliptical version.
Satellite antennas for Dish and DirecTV are not parabolic, but they are
off-center fed and either circular or elliptical. The elliptical version
usually supports a feed that will cover multiple satellites.
C-Band satellites in the U.S. Domestic arc are normally spaced
two degrees apart, with some at 4 degrees spacing.
DBS (Direct Broadcast Service) i.e. Dish and DirecTV, satellites
are spaced 9 degrees apart. Clusters of satellites can be parked
at one location to supply additional capacity for spot beam coverage.
DBS service is located in the Ku-Band.
More info at:
In a message dated 10/9/2014 4:17:20 P.M. Central Daylight Time,
andrew at cleverdomain.org writes:
You pick up satellite TV with a parabolic dish that points at one spot
in the sky where the geostationary satellite lives. A sun outage
happens when the sun wanders into the focus and overloads the receiver
with noise that drowns out the satellite signal (at least, it raises
the noise floor enough that you can't receive the high bitrates needed
for a TV picture).
You pick up GPS with a whole-sky antenna that receives signals from
the constantly-moving swarm of GPS satellites. It undoubtedly receives
some noise from the sun, but the only factor in how much of that you
get is the sun's elevation above the horizon. It's not really relevant
whether the sun is "aligned with a satellite" or not. Even if it was,
the satellite would be somewhere else a minute later. :)
On Thu, Oct 9, 2014 at 1:40 PM, Bob Stewart <bob at evoria.net> wrote:
> Two days this week, there was a 3 or 4 minute outage on DirecTV as the
sun aligned with the satellite and my dish. So I was wondering what kind of
effect this has on the GPS system and especially timing receivers.
> Bob - AE6RV
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