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| reply to ArrayList
Re: Good riddance So is just about any other broadcast technology. Why do you think that you can't put radio or TV stations on adjacent channels and expect them to coexist?
The only case where you'll see this work is on cable systems, and the only reason it works is because the cable company has to carefully balance the power levels of each carrier so one doesn't overpower the one adjacent to it. In the case of GPS and LightSquared, you have a very strong signal (LightSquared's terrestrial transmitter) broadcasting immediately adjacent to a very weak signal (GPS). It simply won't work. If you want to see this in action, tune to a local radio station, then tune one channel up or down the dial and see how well you pick up a station in a distant city. You simply won't get an interference-free signal. If you have a gain control on your radio, you might be able to turn it down enough so that the radio won't get adjacent channel interference from the local station, but then you likely won't be able to receive the weaker signal.
If you think this problem is easily solved and that it's simply the fault of the GPS industry for not trying, you're either sadly mistaken, or you've stumbled upon a technique that could make you rich beyond your wildest dreams, since every broadcaster and receiver manufacturer will bring you stacks of gold bars for such a technology. | |
 ArrayListnetbus developerPremium
join:2005-03-19
Evanston, IL
 ·Comcast
| "Costs" is the reason that they waste spectrum. If they made precision equipment, they could get away with using frequencies adjacent to each other more often. Industry doesn't want to do this because it would cost them more to develop the technology.
I understand the reasoning behind it. However, I don't think that I am asking for too much when I say that we can achieve it. | | |
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| I'm sure that, if you spend enough on the receivers, you could realize some gains, but how much will it cost? Maybe you can build a consumer-grade GPS receiver that would be less susceptible to interference from LightSquared's network for some amount over what they cost now, but, at some point, it isn't economically viable to do so.
But, even if there are gains to be realized, that also applies to LightSquared. After all, if their receivers can be made more sensitive, then they could use lower-powered transmitters, which would reduce their effect on GPS. So, unless their receivers are the model of efficiency, then they're having to transmit with more power than necessary, which is creating unnecessary interference with GPS.
But, IMHO, in LightSquared's case, it comes down to a company wanting to do things on the cheap. If they wanted to build this network, did they bid in the AWS auctions a few years ago? What about the 700 MHz auctions? As I recall, the D block didn't even sell. It would have made more sense to go for some of these frequencies instead of trying to use the spectrum they have now. And, really, they aren't out of the game anyway. Why not use low earth orbit satellites? That should be an option still on the table for them. | |
jdmm72
join:2002-02-12
Nitro, WV Reviews:
·Suddenlink
| reply to ArrayList
Even the best designed band-pass filter will does not produce sharp contrasts across the close frequencies. You have to balance the loss of the original signal with the sharpness of the curves of allowed outside frequency. Making the curves on the outer bands costs of the recieved freqs, not money.
I got an idea, take some Electrical Engineering classes and design that sharp band-pass filter, and you'll rake in the dough. The band passes are idealised as a trough, but in reality, the filtering effect to near freqs are not straight up and down, but actually go at an angle. | |
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