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$DAYJOB is about deploying satellite equipment. > Are these satellites in geosynchronous orbit? Yes. Satellites in other orbits require tracking antennas. A t
by plq 9y ago
$DAYJOB is about deploying satellite equipment.
> Are these satellites in geosynchronous orbit?
Yes. Satellites in other orbits require tracking antennas. A typical one has a four-figure cost at the very least. And if you need uninterrupted connection, you need to have at least two of them, one for tracking the one that sets, and another for tracking the one that rises.
> I'm willing to bet that satellite downlink performance degrades in bad weather
Ku band, as deployed, is highly resilient to bad weather. The SNR will drop, sure, but it will be well above the threshold where it will be unintelligible to the receiver. These things are designed with worst weather conditions in mind. If ever you lost satellite tv during bad weather, that's due to your antenna shaking because of the wind, not rainfade.
DVB-S2 in particular supports adaptive coding modulation (ACM). The standard supports between 4psk and 32psk which can be changed by the ground station when fade is detected in their reference terminals scattered around the footprint region.
You can't really do that for TV links where the bandwidth allocation is more-or-less constant, but you can definitely change modulation for data links which are actually designed to handle such fluctuations in available bandwidth.
- schiffern 9y ago>If ever you lost satellite tv during bad weather, that's due to your antenna shaking because of the wind, not rainfade. Huh, my observations have been different. I lose TV even before the rain and wind starts (trees make any wind quite visible), just because the dense dark rain clouds are blocking the signal path. The rain typically starts a couple minutes later. For digital TV there's an incentive to maximize bandwidth. So they're going to trade off signal:noise to get 99.99% (1-10 minutes/mo), but not 99.99999%. Especially since as you say, the wind will result in some signal interruptions anyway!
- Moru 9y agoYou might not have the most optimal angle on your satellite antenna so it's very sensitive.
- deleted 9y ago[deleted]
- ficklepickle 9y agoYes, very likely. I used to install and service satellite TV systems. You probably have low signal strength to begin with. If not, perhaps there is a tree that only blocks the signal when it's windy. I once had a customer that lost signal in the rain. After much investigation, I found a splice in the cable...in the gutters, which filled with water when it rained.
- plq 9y ago> So they're going to trade off signal:noise to get 99.99%, but not 99.99999%. Depends on where you are in the footprint as well, but of course, totally forgot about the suits. I should have said it's entirely possible to make Ku withstand the worst weather conditions known to mankind, which is not the case for Ka. Trivia: Ku stands for K-under, and Ka stands for K-above, where K-band is IIRC something between 18-27 GHz. Electromagnetic transmissions in this spectrum are absorbed by water vapour, so it's a very bad idea to use this spectrum for satellite. Again IIRC, above 70Ghz, the atmosphere stops being radio-transparent. Ka is way more efficient, but you need a ground station, a satellite and modems that are built from ground up to cope with rainfade. The tricks that work with Ku won't work with Ka.
- baq 9y agoAny comments about three upcoming massive constellations from SpaceX, oneweb, etc. and their pizza box antennas?
- dghughes 9y ago>If ever you lost satellite tv during bad weather, that's due to your antenna shaking because of the wind, not rainfade. I wonder if thats why at my old job I was required to go onto the roof of a four story building to check the dish. The dish sat on old railway ties on a wavy roof. I had to jump from one roof to another it was an L-shaped part of the roof where two buildings joined. I jumped onto a slanted icy roof in winter with a 50 foot drop to a parking lot.