[time-nuts] Sun Outage

[W4wj at aol.com]

Hello all...
 
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:
 
https://docs.google.com/presentation/d/1eNMYmcNIxRFpK1PY0GqbvOfvNfzRra4fHxs8
A4hSy7o/preview#slide=id.p18
 
 
73
Don
W4WJ
 
 
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. :)

Andrew

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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