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Comment: Re:Helping out google's algorithm (Score 1) 70 70

Yeah, that "new law" one is f'ing annoying. It's been a "new law" since, uhm, for as long as I've been buying insurance? News flash: You pay different insurance rates based on your driving profile! WOW. They've started changing up the wording with other non sequiturs, but it's the same crap ad. (Why would the DMV give two shits about how much I'm paying for insurance?)

Comment: Re:Better get those lobbyists ready, Comcast (Score 1) 98 98

When Comcast is looking as a wonderful alternative to me right now compared to the absolutely miserable experience I have with Century Link, I can see at least for my community that this will indeed be some realistic competition for terrestrial ISPs. All they have to beat is $100 per month for more than 800 kilobits/s of service to be economically viable for my family.

Yes, where I live internet service is that crappy. The data gets through, but it is insanely slow and often is far less than 800 kilobits in terms of typical bandwidth... so much so that even dial-up modems seem to have more throughput. I don't exactly live in a major metro area, but it is still a minor city with a population of about 200k people that has fiber optic links into the area that can sustain much higher bandwidth to ordinary households than currently is the case.

I am pretty certain that these terrestrial carriers will be finally upgrading their equipment and be competitive once these alternative networks start to become common place as well.

Comment: Re:Fuck the FCC (Score 1) 98 98

And it is through the International Telecommunications Union (ITU) that most countries coordinate the usage of global spectrum usage. This includes the USA, particularly with regards to almost anything having to do with spaceflight where you have spectrum usage that crosses international boundaries... like will most definitely happen in the case of this satellite constellation.

In the USA, you work through the FCC to make those ITU filings though.

Comment: Re:4000 (Score 3, Interesting) 98 98

I'd wager that financial market trading traffic alone could pay for a significant portion of this bill at super premium rates, especially overseas traders. Not to mention traffic from ships, planes, rural 1st world locations all paying a premium. They can implement zone pricing pretty easily because they will always be able to able to triangulate a transmission down to the inch. With a network that dense it would greatly surpass the accuracy of the existing GPS constellation.

I had not thought of that idea before in terms of a potential customer for this set-up. That is an excellent point. Iridium could have been used for something like this (which also has a digital data component), but given the technology capabilities available at the time Iridium was being built, they could only get about 4800 baud for individual customers... something that makes the bandwidth latency sort of irrelevant. High bandwidth and low latency combined with global coverage would indeed be a good customer.

The major competitor to this concept in that regard is an even older technology though, mainly the 19th Century concept (updated to using 21st Century materials) of the cable laying ship. An awful lot of fiber cable has been laid down across all of the oceans of the world between major cities. It is only when you can't access that fixed terrestrial network that something of this nature really becomes useful (as you've mentioned).

As a means to deliver that last mile architecture, it really opens up possibilities.

Comment: Re:To all you Obama supporters (Score 2) 165 165

The net result of appealing to the FISA Court in this situation more or less means that the issue will be forced into the U.S. Supreme Court. That is one place where even the FISA Court must follow precedent, or else be taken for what it has become as an extra branch of the government answerable to nobody.

To me, that even risks the potential of having the FISA Court itself ruled unconstitutional and a whole can of worms that the Obama administration really doesn't want opened. While I think it is unlikely that SCOTUS will go that far (no matter how I would love to see that happen) it could very well be that some strong oversight by SCOTUS might happen, which has the ability to run the judiciary.

It also opens civil litigation opportunities if somebody wants to be a real jerk about this, again depending on whatever the nine justices want to see done. While perhaps the weakest of the three branches of government, they do have some bite and can demonstrate to Obama and in particular set a precedent for future presidents that he shouldn't dismiss judicial actions so casually.

Comment: Re:Surprised? (Score 1) 98 98

80-bit floats are not available on any platform other than x86

The 80-bit long double is also available on the 68881, 68882 coprocessors and later 68K family members that incorporate the FPU. The Itanium also supports the 80-bit format.

But yeah... those aren't particularly common these days.

Comment: Re:Tesla enables Edison to win the endgame? (Score 1) 597 597

I said as much above.

In an AC system, that current is continuously changing, so those transmission lines are continuously radiating away some amount energy. But that's not all. If there are any conductors nearby, those E-M waves can induce a current in those conductors, and the resulting E-M waves from that induced current can drag on the AC line further. This mutual induction is how transformers work. But, along an AC transmission line, unwanted coupling results in transmission losses. So, an AC system has a built in, inherent source of losses in the alternating current itself.


In a DC system, with a fixed, perfectly resistive load, the current doesn't change, so there's no radiative losses. In the real world, though, the loading on the system is continually changing, so the actual current demand on the DC system will vary over time, and some energy will be radiated away. To some extent that can be filtered, but that's limited by the amount of storage you can put near the ends of the transmission.

Comment: Re:capacitance loss (Score 1) 597 597

Capacitors store energy, they don't dissipate it. Likewise with inductors.

Transmission lines represent both capacitive and inductive loads simultaneously. The capacitance, inductance, resistance of the transmission line together combine to form the characteristic impedance of the line. (Ok, there's one additional term: the conductance of the dielectric between the conductors. But, for high voltage transmission lines that are widely separated, this term is effectively 0.)

The characteristic impedance of a transmission line is of primary importance for determining the ideal load impedance for the line. In an impedance matched system, the maximum power will be transmitted to the load with no reflections.

Reflections can cause a phase shift between voltage and current, making a transmission line effectively look reactive or inductive. (See surge impedance loading.) This can be corrected for in the same ways as reactive or inductive loads by adding capacitance or inductance elsewhere.

If the load itself is reactive or inductive then you can get reactive power transfer. Reactive vs. inductive is in some sense a matter of sign; in one, current leads voltage, in the other current lags voltage. In both cases, current is out of phase with voltage and that's the problem to be solved.

Reactive power doesn't transmit any actual power to the load, but it still sends current through the system. Current is subject to ohmic losses (thanks to our friend I*I*R). Sending current without delivering real power subjects you to losses without any benefits.

In general, the capacitance of the transmission line itself isn't the culprit on its own. Rather, if you have a reactive load (either capacitive or inductive), or you have imperfect impedance matching between the load and the transmission line, you can get current flowing through your wires that isn't driving a load. That excess current incurs plain ol' resistive losses.

There is one way high capacitance can cause real problems for transmission line management, though. The rate of propagation of waves through a conductor slows in proportion to the square root of the product of the inductance and the capacitance. So, for a highly capacitive line, reflections move slowly through the system, and it becomes more difficult to compensate for transients. That seems to be the real bugbear for buried high-capacitance lines. Again, you're not losing to the capacitance directly, but rather to the knock on effects that lead to poorly compensated reflections and reactive power transfer in the system.

(Dr. Jetton, if you're reading this... EE305 may have been 20 years ago for me, but I haven't completely forgotten it. And Dr. Schertz... I didn't completely forget my T-line theory either. I wouldn't be surprised if either of you would point out flaws in my summary above.)

Comment: Re:Premature (Score 1) 597 597

I used 5v as an example as the linked article spoke specifically of running 5V and 12V everywhere. I agree that you really want a higher voltage for distribution. 48V goes a long way, although it still requires quite a lot more copper than 110V or 240V for the same power carrying capacity. (About 5x if I did my math correctly.)

Now, if those in-wall adaptors could store some charge locally (small capacitor bank), and you didn't have to wire for peak current, only sustained current, maybe you could get away with smaller wiring that way. I'm skeptical.

"Time is an illusion. Lunchtime doubly so." -- Ford Prefect, _Hitchhiker's Guide to the Galaxy_