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Why can't we just greatly improve the signal strength at source by an order of magnitude? Like I know the new satellites can use beam forming to increase power

Why can't we just greatly improve the signal strength at source by an order of magnitude? Like I know the new satellites can use beam forming to increase power for some large area for military use but it looks like even so total power is about ~500W right now. What's stopping us from deploying 10KW sats?

dralley 6y ago
>Why can't we just greatly improve the signal strength at source by an order of magnitude? Like I know the new satellites can use beam forming to increase power for some large area for military use but it looks like even so total power is about ~500W right now. What's stopping us from deploying 10KW sats? Even assuming that the very smart and capable people who developed GPS haven't thought about that already, there is zero-point-zero percent chance that the government will (or should) turn 24 satellites that cost 500 million dollars each into very expensive flying paperweights, for the benefit of some tiny 5G startup.
spiorf 6y ago
Deploying a 10KW sat is not a problem. Replacing a whole fleet just to keep it operating the same way as before is.
madengr 6y ago
Supplying the power to the satellite, and getting the heat out. The RF amps are at most 50 % efficient, so you are dissipating 1/2 the input power as heat.
joecool1029 6y ago
> Like I know the new satellites can use beam forming to increase power for some large area for military use No, what you think you 'know' is plain wrong. Usually when discussing satellites, we're talking about a directional antenna that focuses a spot or wide beam for broadcast. A spot beam allows you to target a particular region, DirecTV uses spot beams to provide local broadcasts to general regions of the US. The military uses M-code shit on GPS with a directional antenna for the same sort of use case. Beam forming is a different concept where you get creative with multiple antennas broadcasting at once and exploit signal cancellation to improve the data rate by shifting the phase between them. It does increase your received signal but relies on the receiver transmitting information back to the satellite (which is not going to happen for GPS, at least not the vast majority of consumer equip). Beam forming discussed on HN just last month: https://news.ycombinator.com/item?id=22784132 https://news.ycombinator.com/item?id=22784132 > What's stopping us from deploying 10KW sats? Sat power is around and above that already, it doesn't make sense to increase the spot transponder ERP too much or you end up with issues like interference with adjacent bands since RF gets trickier to filter the higher the power it gets. Keep in mind a comm satellite usually has lots of transponders using maybe 100-500W each, so it adds up to some geosynchronous ones being like 20kW total consumption. Smaller LEO ones obviously not going to be close to that. GPS released a paper about interfering with itself: https://www.gps.gov/multimedia/presentations/2010/10/ICG/betz.pdf https://www.gps.gov/multimedia/presentations/2010/10/ICG/bet... Communications history is littered with failure stories of people who wanted to throw power at the problem, when they only needed to find ways to listen better.
- andromeduck 6y ago
  Thanks that's actually helpful. I did some more reading and it looks like it is as you say, the new military transmitters are directional and steerable, beam forming done on the receiving side. But still it seems that power is still part of the solution given the increased power density of the new military antennas. I guess what I'm wondering is why they can't just reserve more band, move to regional antennas for whatever other technologies in addition to fighting polluters/jammers/spoofers and noisy neighbors. Or is that the plan?

dralley 6y ago

>Why can't we just greatly improve the signal strength at source by an order of magnitude? Like I know the new satellites can use beam forming to increase power for some large area for military use but it looks like even so total power is about ~500W right now. What's stopping us from deploying 10KW sats? Even assuming that the very smart and capable people who developed GPS haven't thought about that already, there is zero-point-zero percent chance that the government will (or should) turn 24 satellites that cost 500 million dollars each into very expensive flying paperweights, for the benefit of some tiny 5G startup.

spiorf 6y ago

Deploying a 10KW sat is not a problem. Replacing a whole fleet just to keep it operating the same way as before is.

madengr 6y ago

Supplying the power to the satellite, and getting the heat out. The RF amps are at most 50 % efficient, so you are dissipating 1/2 the input power as heat.

joecool1029 6y ago

> Like I know the new satellites can use beam forming to increase power for some large area for military use No, what you think you 'know' is plain wrong. Usually when discussing satellites, we're talking about a directional antenna that focuses a spot or wide beam for broadcast. A spot beam allows you to target a particular region, DirecTV uses spot beams to provide local broadcasts to general regions of the US. The military uses M-code shit on GPS with a directional antenna for the same sort of use case. Beam forming is a different concept where you get creative with multiple antennas broadcasting at once and exploit signal cancellation to improve the data rate by shifting the phase between them. It does increase your received signal but relies on the receiver transmitting information back to the satellite (which is not going to happen for GPS, at least not the vast majority of consumer equip). Beam forming discussed on HN just last month: https://news.ycombinator.com/item?id=22784132 https://news.ycombinator.com/item?id=22784132 > What's stopping us from deploying 10KW sats? Sat power is around and above that already, it doesn't make sense to increase the spot transponder ERP too much or you end up with issues like interference with adjacent bands since RF gets trickier to filter the higher the power it gets. Keep in mind a comm satellite usually has lots of transponders using maybe 100-500W each, so it adds up to some geosynchronous ones being like 20kW total consumption. Smaller LEO ones obviously not going to be close to that. GPS released a paper about interfering with itself: https://www.gps.gov/multimedia/presentations/2010/10/ICG/betz.pdf https://www.gps.gov/multimedia/presentations/2010/10/ICG/bet... Communications history is littered with failure stories of people who wanted to throw power at the problem, when they only needed to find ways to listen better.

andromeduck 6y ago
Thanks that's actually helpful. I did some more reading and it looks like it is as you say, the new military transmitters are directional and steerable, beam forming done on the receiving side. But still it seems that power is still part of the solution given the increased power density of the new military antennas. I guess what I'm wondering is why they can't just reserve more band, move to regional antennas for whatever other technologies in addition to fighting polluters/jammers/spoofers and noisy neighbors. Or is that the plan?