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No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
wrote in : That is for energetic stuff floating around in some particular place. If you were causght in a CME it would be a lot hotter than that, but again that is stuff. The background temperature of space is 2.7 K. Ok, I just can't stop thinkling that stuff might get around out there in ways that are hard to predict, or sheild from. Get over it; we found out what's out there about a half century ago. -- Jim Pennino |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
rickman wrote in : You are aware that a standing wave still moves up and down, no? Sorry about this.. even after my last post, I have a thought I can't drop easily. A few years ago someone showed me a speaker cone in a video, driven by AC current, and it had ferrofluid on it, but I think there was soem comment that any thixotropic fluid will do. It had peaks and troughs, in a sort of semi-random 2D form across the cone that held it. These peaks and troughs did not oscillate up and down on the spot, they stood rigid as merings peaks after drying in an oven. (Actually they did shift a little, but not a lot, and that was mainly due to erratic vibrations in the whole doings.) Anyway, would that effect not also be called a standing wave? It would be called a scene from The Big Bang Theory; a speaker covered with plastic wrap with a water and corn starch mixture. -- Jim Pennino |
No antennae radiate all the power fed to them!
On 11/2/2014 5:49 PM, Lostgallifreyan wrote:
rickman wrote in : No, the topic was antenna radiating all the power fed to them. Specifically, doing it efficiently. :) Just being hard to match. Never mind the other bits, beginning to look like old ground already today. What I might be missing about my comment on some body at some temperature being limited in its rate of dissipation might be flawed anyway. Never mind the risk of confusion between an antenna's radiation resistance and what I'm trying to get at, there's another angle to this... Am I wrong? Could it be that just as an antenna is efficient regardless of size, IF you can feed it all the energy you're trying to transmit, is it also true that regardless of size, that hot body will also equally transmit all its heat? In other words, is the 'limit' analogous to matching, as in getting the heat from the bulk volume out to its surface? I'm hoping that answer(s) to this one might help solve a heap of confusion for me.. Hmmm... All things emit energy according to their temperature and their surface emissivity. All things also absorb energy according to their surface emissivity. Both processes are going on at all times. So an object loses or gains heat depending on its temperature and the temperature of the environment. That delta temperature sets the rate along with the surface emissivity. In space with the environment near absolute zero (ignoring radiation from the sun and other nearby objects) any object's radiation of heat will be near it's maximum potential and limited only by its absolute temperature. So yes, an object will lose heat according to it's temperature and that will be less at lower temperatures. But that doesn't mean a super conductor will warm up unless there is something heating it. -- Rick |
No antennae radiate all the power fed to them!
On Sunday, November 2, 2014 4:31:36 PM UTC-6, Jerry Stuckle wrote:
But if it keeps one direction pointed towards Earth, then it has to roll - one rotation per orbit. Which means the solar panels have to be steerable to some extent for maximum power. I'd have to watch a few full passes to see.. They have multiple cameras aimed in different directions, so I'm not sure if they actually roll once an orbit or not. For some reason, I'm thinking they don't.. Mainly because I don't recall the shuttle as rolling during orbits. They always flew upside down and maybe even backwards in orbit, with the cargo bays aimed at the planet. I think anyway.. I'd have to look into that more. Some cameras seem to aim forward, and some backwards like you are watching out the back of an old nine passenger station wagon. :| |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
On 11/2/2014 6:31 PM, wrote:
On Sunday, November 2, 2014 4:31:36 PM UTC-6, Jerry Stuckle wrote: But if it keeps one direction pointed towards Earth, then it has to roll - one rotation per orbit. Which means the solar panels have to be steerable to some extent for maximum power. I'd have to watch a few full passes to see.. They have multiple cameras aimed in different directions, so I'm not sure if they actually roll once an orbit or not. For some reason, I'm thinking they don't.. Mainly because I don't recall the shuttle as rolling during orbits. They always flew upside down and maybe even backwards in orbit, with the cargo bays aimed at the planet. I think anyway.. I'd have to look into that more. Some cameras seem to aim forward, and some backwards like you are watching out the back of an old nine passenger station wagon. :| Which means it rolls once per orbit. Otherwise it wouldn't be able to keep the same side facing the earth. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
On 11/2/2014 6:11 PM, wrote:
Jerry Stuckle wrote: On 11/2/2014 3:58 PM, wrote: Lostgallifreyan wrote: wrote in : Apples and oranges; we already know what will happen if one were to build an antenna from a superconductor. Fire up EZNEC and set material loss to zero; done. Yeah, anyone with a map could say a great deal about the shape of West Africa based on ocean travel. Again, apples and oranges as we know EXACTLY and in DETAIL what would happen. My point isn't so much about antennas, as about exploring the easy availability of cold environments for superconductors in space. Easy availability measured in thousands of dollars an ounce to get stuff there. Not having to lug heavy coolers up there might be an offer someone cannot refuse, and that someone might come back with all kinds of discoveries, things no models or predictions are going out there to find. The only thing that makes a superconductor different is the lack of resistance. We already know exactly what that means and what we would do with them if room temperature superconcductors were available. Here are a couple of things: electric motors and generators that would be very close to 100% efficient, small, light, and lossless power transmission lines, lossless transformers, big honking magnets. It's a little more than just no resistance. For instance, superconductors will "reflect" (for lack of a better word) a magnetic field. That's now a superconducting disk will levitate over a magnetic field. So just setting the resistance to zero doesn't necessarily cut it. There are other things to consider which EZNIC may not handle properly. Such as? In regards to magnetic levitation, a super conductor is a perfect diamagnet due to the Meissner effect. None of that has anything to do with antennas. http://hyperphysics.phy-astr.gsu.edu...ds/maglev.html http://en.wikipedia.org/wiki/Magnetic_levitation Are you sure? I haven't seen anything one way or the other on it - although I'm sure it's been studied. Can you point at some studies to that effect? -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
On 11/2/2014 6:17 PM, wrote:
Jerry Stuckle wrote: On 11/2/2014 4:55 PM, wrote: Lostgallifreyan wrote: wrote in : There is no undiscovered magic in superconductors. There was no magic in any of the materials used for Gemini and Apollo either, but countelss things were learned just by using them out there. Care to name a few specifically from Genini and Apollo? And BTW, 99.9% of the materials used is aluminum. Much of the medical monitoring technology came out of the early space program, for one thing. So did advances in propulsion systems and remote controls (more than just model planes and cars) for another. True, but none of that came from throwing the stuff up into space just to see what would happen. No, but they all came from the space race (Mercury, Gemini and Apollo programs) - which was your question. And since then, there have been all kinds of experiments on various orbiting objects such as MIR, Skylab, the space shuttle and ISS. Many discoveries are coming out of it - although I don't know offhand what's been put to use yet, since there is no manufacturing in space. But thinks like perfectly round ball bearings and new ways to make pharmaceuticals come to mind. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
rickman wrote in :
Recorded temperatures have always set new records. Just considering one location, there are 365 days in a year and so 730 high and low records to test. We have been recording temperatures for roughly 200 years. What are the chances we *won't* set a new record for one of those dates in a given year? True, it's no great deal intself. And given the Maunder Minimum soem big excursions can be expected, especially as the sun isn't following its usual 11-year pattern. On the other hand I remember people asking me in 1983 about glonal warming, and me insisting that it did not just mean warmer, but wetter, stormier, as well. There's no doubt that compared to thiry years ago this has happened across most of thwe world. For a real balance of 'records', we need to know how often the record for quietest, or closest approach to average, conditions occured, and I have never heard the like. :) Generally, if news is not exciting, it is not considered as news. Also, even when we had unusual cold recently, it is arguable that climate conditions don't cause a strong enough gradient to keep a strong division of temperature with lattitude, and similar things can be said about the wandering of the jet stream. Too many things look new, an the rate of broken records is increasing when it ought to be decreasing if things were generally stable. |
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