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No antennae radiate all the power fed to them!
On 11/1/2014 7:59 PM, wrote:
rickman wrote: On 11/1/2014 5:31 PM, wrote: rickman wrote: On 11/1/2014 1:03 PM, wrote: gareth wrote: Ignoring, for the moment, travelling wave antenna, and restricting discussion to standing wave antennae ... An antenna is an antenna. Deep thoughts... A wave is launched, and radiates SOME of the power, and suffers both I2R losses and dielectric and permeability losses associated with creating and collapsing the near field. Nope, voltage is applied to an antenna causing currents to be created which in turn cause an electromagnetic field to be created. As antennas are made of real materials they have a resistance and the current through that resistance leads to losses. I thought there were *real* materials with no resistance. Isn't that what a superconductor is? Well, to be pendatic, there are no real materials with zero resistance that can be used to build antennas. Why can't you build an antenna with a superconductor? As all the current existing superconductors require a bunch of supporting equipment to keep them cold, they can't be used for antennas. Really? What is the problem? There are super conductors at liquid nitrogen temperatures and you can have that sitting in a flask on your desk. Why couldn't that cool an antenna? Once you remove the I*R losses, you don't even have to worry about the radiated power heating the N2. If one were realy determined to do it, one could build the antenna in a non-metalic container of some sort and keep the container filled with LN2. I think you are confusing need with practicality. There is nothing to stop you from making a superconducting antenna. There just isn't a need for it unless you live in Gareth's world. Hmmm... wasn't that a movie? Gareth's World? It is not need versus practicality, it is practicality period. If room temperature superconductors are ever invented... However, those are like a cure for the common cold, practical fusion power, and peace in the Middle East, all just around the corner for the past half century or so. I've never heard anyone say either a cure for the common cold or fusion was "around" the corner. I've never heard anyone say at all that peace is expected in the middle east. You must not be very old then... No, I'm not, I'm much less than a century old. I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". You mean other than the shade screen? You do understand two big problems with space stuff is how to get rid of any generated heat and Solar heating? Is there a lot of solar heating near Jupiter? I didn't realize... In any case, why? I^2R losses only become significant in very small antennas and there is all the space you could ask for in space to build an antenna. You snipped the part of my post that addressed your questions. It would be better if you read posts before trimming them. -- Rick |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
rickman wrote:
On 11/1/2014 7:59 PM, wrote: rickman wrote: On 11/1/2014 5:31 PM, wrote: rickman wrote: On 11/1/2014 1:03 PM, wrote: gareth wrote: Ignoring, for the moment, travelling wave antenna, and restricting discussion to standing wave antennae ... An antenna is an antenna. Deep thoughts... A wave is launched, and radiates SOME of the power, and suffers both I2R losses and dielectric and permeability losses associated with creating and collapsing the near field. Nope, voltage is applied to an antenna causing currents to be created which in turn cause an electromagnetic field to be created. As antennas are made of real materials they have a resistance and the current through that resistance leads to losses. I thought there were *real* materials with no resistance. Isn't that what a superconductor is? Well, to be pendatic, there are no real materials with zero resistance that can be used to build antennas. Why can't you build an antenna with a superconductor? As all the current existing superconductors require a bunch of supporting equipment to keep them cold, they can't be used for antennas. Really? What is the problem? There are super conductors at liquid nitrogen temperatures and you can have that sitting in a flask on your desk. Why couldn't that cool an antenna? Once you remove the I*R losses, you don't even have to worry about the radiated power heating the N2. If one were realy determined to do it, one could build the antenna in a non-metalic container of some sort and keep the container filled with LN2. I think you are confusing need with practicality. There is nothing to stop you from making a superconducting antenna. There just isn't a need for it unless you live in Gareth's world. Hmmm... wasn't that a movie? Gareth's World? It is not need versus practicality, it is practicality period. If room temperature superconductors are ever invented... However, those are like a cure for the common cold, practical fusion power, and peace in the Middle East, all just around the corner for the past half century or so. I've never heard anyone say either a cure for the common cold or fusion was "around" the corner. I've never heard anyone say at all that peace is expected in the middle east. You must not be very old then... No, I'm not, I'm much less than a century old. And I'm the better part of one and heard all of those many times now. I forgot to add true artificial intelligence to the list. I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". You mean other than the shade screen? You do understand two big problems with space stuff is how to get rid of any generated heat and Solar heating? Is there a lot of solar heating near Jupiter? I didn't realize... Not a lot but the point is cooling options in space are limited and you said nothing about where in space. In any case, why? I^2R losses only become significant in very small antennas and there is all the space you could ask for in space to build an antenna. You snipped the part of my post that addressed your questions. It would be better if you read posts before trimming them. I snipped nothing when I responded. -- Jim Pennino |
No antennae radiate all the power fed to them!
Jeff Liebermann wrote:
On Sat, 01 Nov 2014 18:47:32 -0400, rickman wrote: I think you are confusing need with practicality. There is nothing to stop you from making a superconducting antenna. There just isn't a need for it unless you live in Gareth's world. Hmmm... wasn't that a movie? Gareth's World? (...) I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". You don't need to go to outer space to see cryogenic radios in operation. You can see space a lot better with a cryogenic radio. -- Jim Pennino |
No antennae radiate all the power fed to them!
rickman wrote:
On 11/1/2014 8:18 PM, wrote: Wayne wrote: snip I was going to point out to Gareth that he is describing behavior in an antenna system, not an antenna. I doubt he will EVER understand the difference. But, I'm done now. No more. It does become tiresome correcting the same nonsense over and over again. Then there is no need at all to reply, no? Other than to prevent a casual reader from thinking his nonsense is reality, not really. Well, that and I really have a thing about deflating long winded gas bags. -- Jim Pennino |
No antennae radiate all the power fed to them!
On 11/2/2014 1:24 AM, wrote:
rickman wrote: On 11/1/2014 7:59 PM, wrote: rickman wrote: On 11/1/2014 5:31 PM, wrote: rickman wrote: On 11/1/2014 1:03 PM, wrote: gareth wrote: Ignoring, for the moment, travelling wave antenna, and restricting discussion to standing wave antennae ... An antenna is an antenna. Deep thoughts... A wave is launched, and radiates SOME of the power, and suffers both I2R losses and dielectric and permeability losses associated with creating and collapsing the near field. Nope, voltage is applied to an antenna causing currents to be created which in turn cause an electromagnetic field to be created. As antennas are made of real materials they have a resistance and the current through that resistance leads to losses. I thought there were *real* materials with no resistance. Isn't that what a superconductor is? Well, to be pendatic, there are no real materials with zero resistance that can be used to build antennas. Why can't you build an antenna with a superconductor? As all the current existing superconductors require a bunch of supporting equipment to keep them cold, they can't be used for antennas. Really? What is the problem? There are super conductors at liquid nitrogen temperatures and you can have that sitting in a flask on your desk. Why couldn't that cool an antenna? Once you remove the I*R losses, you don't even have to worry about the radiated power heating the N2. If one were realy determined to do it, one could build the antenna in a non-metalic container of some sort and keep the container filled with LN2. I think you are confusing need with practicality. There is nothing to stop you from making a superconducting antenna. There just isn't a need for it unless you live in Gareth's world. Hmmm... wasn't that a movie? Gareth's World? It is not need versus practicality, it is practicality period. If room temperature superconductors are ever invented... However, those are like a cure for the common cold, practical fusion power, and peace in the Middle East, all just around the corner for the past half century or so. I've never heard anyone say either a cure for the common cold or fusion was "around" the corner. I've never heard anyone say at all that peace is expected in the middle east. You must not be very old then... No, I'm not, I'm much less than a century old. And I'm the better part of one and heard all of those many times now. I forgot to add true artificial intelligence to the list. I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". You mean other than the shade screen? You do understand two big problems with space stuff is how to get rid of any generated heat and Solar heating? Is there a lot of solar heating near Jupiter? I didn't realize... Not a lot but the point is cooling options in space are limited and you said nothing about where in space. lol. No, cooling in space is very easy. Heat radiates quite well. That's why they can power the electronics with RTGs so well. In any case, why? I^2R losses only become significant in very small antennas and there is all the space you could ask for in space to build an antenna. You snipped the part of my post that addressed your questions. It would be better if you read posts before trimming them. I snipped nothing when I responded. You are right, it is all there. -- Rick |
No antennae radiate all the power fed to them!
rickman wrote in :
What? For a wave to have a "bulge" above the top of the tank means there is a trough well below the top of the tank. The amount of liquid does not change because you make waves in the tank. I didn't say it did. Anyway, I've been looking at images on Google, apparently the single half-wave form is concave in a tank of liquid, not convex. Maybe that too is possible, I don't know. If it is, then you can add liquid to what was a brim-fill tank before it overflows once the wave is set up, which would indicate that a form of storage has been set up. Look at it another way... Any standing wave shape in a tank will not be flat, and when the small amount of energy maintaining it is stopped, it will give back energy until it is flat, so it looks like a way to store energy. A 'tank ciruit' has to have a way to store energy too. (As to why I go into these apparently off-topic variations, it's because I think a person can know something by being very specific, but probably cannot understand it unless they look at as many other things as possible in which similar action occurs.) |
No antennae radiate all the power fed to them!
Jeff Liebermann wrote in
: Not quite. If you apply energy to a resonant circuit (electrical or mechanical), that then remove the input, you'll get a damped wave (i.e. exponential decay) output where the rate of decay is determined by the losses in the system. You could build a transmission line oscillator, which would exhibit some rather small damped wave output when turned off, but in most cases, there's no connection with reflected or standing waves because there is usually no transmission line. Well, doesn't that still mean there's energy there to power that decay? I get the exponential bit (had to explore that a lot to code a synth. :) so the energy never entirely vanishes, sort of like half-life in fissile materials. Point taken about usually no transmission line. I remember CB'ers talking of SWR meters and aiming for as little standing wave as possible. That seems to go with what Jim (Pennino) said about not having a standing wave without a transmission line. Might as well be part of the problem. What I do in my spare time. I recorded these in about 1998. Please forgive my screwups, plagerism, lack of coherent style, sloppy fingering, etc: http://802.11junk.com/jeffl/music/ Nice. Though you do what I tend to do, caught in a singular sort of chord sequence, expression, whatever it is. I got it from listening to Tangerine Dream. It's a nice trap (and yours is more elegant than mine too) but it is a trap. I found a way out of it though, if I can make the effort and maintain the habit... When walking, I hum, or whistle, and the tunage is far more varied than when I'm in front of an instrument. I have a small USB memoery thinger with audio recording (and annoyingly short battery life) that I usually fail to carry with me. Shame, because a couple of days ago I improvised for about a half hour on a Cuban tune, 'Chan Chan', very effectively, and had never done that before. The more I learn about Beethoven and Schubert, the more I hear about how good they were at improvisation! Most people seem to think that 'vclassical' was all ablout written formalism. Of course it wasn't... it was closer to jazz in the sense that it was about capturing improvisation. Their skill was in doing exactly that. Mozart heard Allegri's 'Misereri' at one sitting, and recalled enough to write it down later. I can't do that, but with a bit of technical help (if I can be bothered to persist in using it), I might make a few things, at least enough to test the instrument I'm trying to byuild. :) I have no web storage, but if you're interested I can try to put three of four bits into a Usenet test binary group somewhere.. They're not very elaborate, just a few very varied ideas. |
No antennae radiate all the power fed to them!
rickman wrote in :
I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". There's still such a thing as radiation resistance, I think, so it wouldn't stay cold even there. Given the size of a body, there's a limit to how fast it can get rid of heat at a given temperature.. I don't know the proper terminology for it though. Anyway, at low tenperature, the rate it can radiate heat is low, so it will quickly warm up out of low-temp superconducting state. |
No antennae radiate all the power fed to them!
rickman wrote in :
No, cooling in space is very easy. Heat radiates quite well. True but to get the best of it you have to have high grade energy to radiate. (High temperatures, short wavelengths). If you could efficiently convert low grade warmth in large amounts, to a small source of incandescent light, you'd improve it. I'm not sure if such a process is easy or practical. To be worth doing, it would have to cost less energy to convert than the difference in that emitted for the two temperatures. It would probably have to use storage too, for long slow inputs, short strong bursts of output, which complicates things. The problem is that low temperature superconductors are way too cool to start with, so the supporting equipment would be as awkward as that on Earth, and likely more so. |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote in
: True but to get the best of it you have to have high grade energy to radiate. (High temperatures, short wavelengths). If you could efficiently convert low grade warmth in large amounts, to a small source of incandescent light, you'd improve it. I'm not sure if such a process is easy or practical. To be worth doing, it would have to cost less energy to convert than the difference in that emitted for the two temperatures. It would probably have to use storage too, for long slow inputs, short strong bursts of output, which complicates things. Never mind what I wrote just now. Can't beat entropy. |
No antennae radiate all the power fed to them!
Jeff wrote in :
...or looking at it another way the dissipation in the radiation resistance is not in the form of heat it is the power radiated into space. Well, I did say I didn't know the terminology. On the other hand, I'm not talking about antenna's radiation resistance. The only thing I'm sure of here is that some body, at some temperature, can not emit heat faster than some rate, and that superconductors in space will warm up too fast to stay superconducting without support to cool them. This discussion looked like it had strayed some way from the earlier talk of antennas and radiation resistance. |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote in
: Well, I did say I didn't know the terminology. I just had a quick look at this: http://en.wikipedia.org/wiki/Radiosity_(heat_transfer) I've decided to just say I don't know and leave it at that. I am not going to try to penetrate that lot. A person could get lost there forever. |
No antennae radiate all the power fed to them!
On 2014-11-02 11:01:54 +0000, Lostgallifreyan said:
Lostgallifreyan wrote in : True but to get the best of it you have to have high grade energy to radiate. (High temperatures, short wavelengths). If you could efficiently convert low grade warmth in large amounts, to a small source of incandescent light, you'd improve it. I'm not sure if such a process is easy or practical. To be worth doing, it would have to cost less energy to convert than the difference in that emitted for the two temperatures. It would probably have to use storage too, for long slow inputs, short strong bursts of output, which complicates things. Never mind what I wrote just now. Can't beat entropy. No, but you *can* use a heat pump to move it somewhere else. -- Percy Picacity |
No antennae radiate all the power fed to them!
Percy Picacity wrote in
: Never mind what I wrote just now. Can't beat entropy. No, but you *can* use a heat pump to move it somewhere else. Yes, sort of what I was getting at, I'm just not sure what qualifies as 'worth it' :) For example, you could store some low grade heat converting to electric charge in batteries. This could then power a hot high current heater to radiate overcoming local ambient heat from solar energy in a space installation. If you had enough shade that would be likely less useful, it might be cheaper to set up large low-grade radiators instead. it seems to me that all kinds of compromises with cost, size, ambient conditions, will rule what actually gets done. Given that laser diodes can radiate a lot of power now, and be small with very low mass, and convert upwards of 30% electrical input to light, they might become part of a compact space-based heatsink. I suspect that 30% will not be nearly enough to be usful in most cases because there will be other, greater losses (laser diodes are some of the most efficient transducers ever made). |
No antennae radiate all the power fed to them!
On 11/2/2014 6:06 AM, Lostgallifreyan wrote:
Jeff wrote in : ...or looking at it another way the dissipation in the radiation resistance is not in the form of heat it is the power radiated into space. Well, I did say I didn't know the terminology. On the other hand, I'm not talking about antenna's radiation resistance. The only thing I'm sure of here is that some body, at some temperature, can not emit heat faster than some rate, and that superconductors in space will warm up too fast to stay superconducting without support to cool them. This discussion looked like it had strayed some way from the earlier talk of antennas and radiation resistance. What would cause the superconductors to warm up? They have no resistance, so it wouldn't be from internal means. And kept shaded, there would be very little external heat applied. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
"Brian Reay" wrote in message
... It is nonsense, they can be no wave in the element due to it being a conductor. He is confusing the I and V plots for waves. OK, I realise now where your confusion has arisen. It is because I was discussing what was necessary to set up a standing wave in the first place, whereas you misunderstood and became confused because you were discussing the state of affairs AFTER the standing wave had been set up. Perhaps if you read posts more carefully and were not so intent on scoring points and abusing those with whom you deliberately disagree? |
No antennae radiate all the power fed to them!
Jerry Stuckle wrote in news:m35chg$mlv$1@dont-
email.me: What would cause the superconductors to warm up? They have no resistance, so it wouldn't be from internal means. And kept shaded, there would be very little external heat applied. Not much, maybe. I just figured that their state would not be stable, that it would take very little, from any source, to heat them to the point where the problem started getting rapidly worse. Maybe it wouldn't be an issue if the superconductor were 'hot' enough. -196°C is 77°C above absolute zero, so maybe some of them will always stay cold enough with nothing but shade. Heat sources might be unexpected though. If a thin wire got hit my a micrometeorite, it would likely get stretched and heated pretty fast. So the question might be what kind of margins exist for safe operation. |
No antennae radiate all the power fed to them!
On 11/2/2014 9:11 AM, Lostgallifreyan wrote:
Jerry Stuckle wrote in news:m35chg$mlv$1@dont- email.me: What would cause the superconductors to warm up? They have no resistance, so it wouldn't be from internal means. And kept shaded, there would be very little external heat applied. Not much, maybe. I just figured that their state would not be stable, that it would take very little, from any source, to heat them to the point where the problem started getting rapidly worse. Maybe it wouldn't be an issue if the superconductor were 'hot' enough. -196°C is 77°C above absolute zero, so maybe some of them will always stay cold enough with nothing but shade. Actually, high temperature superconductors have been found at temperatures as high as -135C. And in the shade, space is very cold, even at Earth's distance from the sun, shaded items are very cold. Even the moon, which will hold some heat, cools to -233C at night time. Heat sources might be unexpected though. If a thin wire got hit my a micrometeorite, it would likely get stretched and heated pretty fast. So the question might be what kind of margins exist for safe operation. I think the odds of this happening between now and the end of the solar system are pretty slim. If a small wire could so easily be hit by a micrometeorite, our satellites, space stations, rockets, etc., all much bigger, would be in deep doo-doo. No, micrometeorites are not very big, but their velocity makes them very dangerous. Energy increases with the square of the velocity, and micrometeorites move very fast. -- ================== Remove the "x" from my email address Jerry Stuckle ================== |
No antennae radiate all the power fed to them!
Jerry Stuckle wrote in
: Actually, high temperature superconductors have been found at temperatures as high as -135C. And in the shade, space is very cold, even at Earth's distance from the sun, shaded items are very cold. Even the moon, which will hold some heat, cools to -233C at night time. I wonder if the ISS might be a place capable of doing tests like these. Parts of that must be in constant shade, so maybe some test of a space-based superconducting antenna is feasible. (I'm not ignoring what Jim said about having space to build a big, normal antenna, it's just interesting that there might be scope now to try this just to see what can be done with it. Also, given the cost of sendign heavy stuff out there, it might be viable anyway if it saves the need to do that so often). I think the odds of this happening between now and the end of the solar system are pretty slim. If a small wire could so easily be hit by a micrometeorite, our satellites, space stations, rockets, etc., all much bigger, would be in deep doo-doo. Ok. :) Besides, never mind stretching, the superconductor would be brittle, probably. Would a swarm of partcles redirected from sun via some magnetic field, passing the antenna wire, be enough to heat it to the point of supercondcuting failure? I have no idea about this, it just seems that there might be a lot of energy, even if thinly distributed.. |
No antennae radiate all the power fed to them!
On Sun, 2 Nov 2014 05:30:14 -0000, wrote:
Jeff Liebermann wrote: On Sat, 01 Nov 2014 18:47:32 -0400, rickman wrote: I think you are confusing need with practicality. There is nothing to stop you from making a superconducting antenna. There just isn't a need for it unless you live in Gareth's world. Hmmm... wasn't that a movie? Gareth's World? (...) I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". You don't need to go to outer space to see cryogenic radios in operation. You can see space a lot better with a cryogenic radio. On the ground, cooling the LNB is easy enough but how do you cool the dish? The LNB is looking at the entire dish, which is sitting there radiating at ambient temperature. Paint is low emissivity white? Incidentally, I tried making my own LNB cooling derangement back in the days of 100K C-band LNB's. Peltier 6 pack beer cooler plumbed with copper ice maker line and an aquarium pump. The signal would look great for about 10 minutes, and then slowly fade away. It seems that cooling also causes water to condense on the "mica" waveguide window. Add a small heater and fan. When I replaced it with a 25K LNB, the cooler and fan went away. At least in outer space, there is no condensation problem. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
Jerry Stuckle wrote in news:m35chg$mlv$1@dont- email.me: What would cause the superconductors to warm up? They have no resistance, so it wouldn't be from internal means. And kept shaded, there would be very little external heat applied. Not much, maybe. I just figured that their state would not be stable, that it would take very little, from any source, to heat them to the point where the problem started getting rapidly worse. Maybe it wouldn't be an issue if the superconductor were 'hot' enough. -196?C is 77?C above absolute zero, so maybe some of them will always stay cold enough with nothing but shade. Heat sources might be unexpected though. If a thin wire got hit my a micrometeorite, it would likely get stretched and heated pretty fast. So the question might be what kind of margins exist for safe operation. The only external heat source in space is the Sun; solution, sun shade. If shaded, things get quite cold in space, cold enough for known superconductors to work. A hit by a micrometeorite would be rare, but likely catastrophic; heat wouldn't be your main problem. But again, the question is why bother? -- Jim Pennino |
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 10:49 AM, Lostgallifreyan wrote:
Jerry Stuckle wrote in : Actually, high temperature superconductors have been found at temperatures as high as -135C. And in the shade, space is very cold, even at Earth's distance from the sun, shaded items are very cold. Even the moon, which will hold some heat, cools to -233C at night time. I wonder if the ISS might be a place capable of doing tests like these. Parts of that must be in constant shade, so maybe some test of a space-based superconducting antenna is feasible. (I'm not ignoring what Jim said about having space to build a big, normal antenna, it's just interesting that there might be scope now to try this just to see what can be done with it. Also, given the cost of sendign heavy stuff out there, it might be viable anyway if it saves the need to do that so often). No, I don't think any part of the ISS is in "constant shadow". I believe it rotates as it orbits the earth, and different parts of it are in the shade at different times. I could be wrong, though - I've never been there :) I think the odds of this happening between now and the end of the solar system are pretty slim. If a small wire could so easily be hit by a micrometeorite, our satellites, space stations, rockets, etc., all much bigger, would be in deep doo-doo. Ok. :) Besides, never mind stretching, the superconductor would be brittle, probably. Would a swarm of partcles redirected from sun via some magnetic field, passing the antenna wire, be enough to heat it to the point of supercondcuting failure? I have no idea about this, it just seems that there might be a lot of energy, even if thinly distributed.. Those particles, although moving quickly, would be too small to have much effect. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
wrote in : But again, the question is why bother? Well, to add to your list of Eternal Questions of the Past Century, you can add that one. :) It's far older actually, and has been asked of air travel, mountian climbing, exploring West Africa, Antartica, and probably bungy jumping. The jury's still out on that last one. The simple answer is: because it hasn't been done, or at least not by the person most wanting and able to do it. A better answer is: to find out what can be learned along the way, given that the destination is a new one. Most of science was built that way. 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. snip more apples and oranges -- Jim Pennino |
No antennae radiate all the power fed to them!
Jerry Stuckle wrote in news:m36209$kk3$1@dont-
email.me: No, I don't think any part of the ISS is in "constant shadow". I believe it rotates as it orbits the earth, and different parts of it are in the shade at different times. I could be wrong, though - I've never been there :) Fair enough. I know that Apollo used to do the 'barbeque roll', but as far as I know there's less need of it on the ISS for whatever reason. Maybe they use the solar panels for shade part of the time, there's a lot of those... Or maybe it's in Earth's shadow often enough to get by... Or maybe it rolls constantly and I just had no idea. About particles, I don't know what sort of quantities there could be, or energies involved, but I'll settle for the realisation that an amount capable of causing heating would be long past rendering an antenna too noisy to use, probably. I suspect heating by remnant of mass coronal ejection might be the least of its worries. :) |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
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. -- Jim Pennino |
No antennae radiate all the power fed to them!
On 11/2/2014 1:33 AM, wrote:
rickman wrote: On 11/1/2014 8:18 PM, wrote: Wayne wrote: snip I was going to point out to Gareth that he is describing behavior in an antenna system, not an antenna. I doubt he will EVER understand the difference. But, I'm done now. No more. It does become tiresome correcting the same nonsense over and over again. Then there is no need at all to reply, no? Other than to prevent a casual reader from thinking his nonsense is reality, not really. Well, that and I really have a thing about deflating long winded gas bags. But that ain't gonna happen. In fact it is exactly these sort of responses that put air in his sails and keeps him going. In the end it makes you look pretty stupid too. Sort of like wrestling a pig. You get all dirty and the pig enjoys it. -- Rick |
No antennae radiate all the power fed to them!
On 11/2/2014 5:02 AM, Lostgallifreyan wrote:
rickman wrote in : What? For a wave to have a "bulge" above the top of the tank means there is a trough well below the top of the tank. The amount of liquid does not change because you make waves in the tank. I didn't say it did. Anyway, What did you mean by, "that tank will hold more liquid that it would if brim full without the wave"??? I've been looking at images on Google, apparently the single half-wave form is concave in a tank of liquid, not convex. Maybe that too is possible, I don't know. If it is, then you can add liquid to what was a brim-fill tank before it overflows once the wave is set up, which would indicate that a form of storage has been set up. You are aware that a standing wave still moves up and down, no? So a trough turns into a crest and vice versa. -- Rick |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
wrote in : The only external heat source in space is the Sun; solution, sun shade. Maybe not. I just did a bit of Googling for 'superconductors in space' minus quotes. There's a lot of statements abotu space missions ended because required helium or hydrogen coolant ran out, Yeah, the coolent ran out for the things that GENERATE a lot of heat and need to be cooled more than radiation can provide. Radiative cooling does not provide for a lot of cooling. and also of space having latent temperatures up to 100K, so a sun shade won't help a lot there with current materials. There really is no such thing as temperature in space as it is a vacuum. Also, show me the 100% efficient sun shade. Maybe the James Webb scope's shield might set some new precedents if that gets launched. Grocery store aluminum foil will come very, very close. Basically, any worth in the idea will come out of some compromise between ambient conditions and new higher temperature superconductors. And if they end up cheaper to lug up there than the current materials for antennas and matching networks, they may get used anyway. Without knowing what materials become available, and the needs for them, we can't assert a lot about what is possible. We already know what is possible. There is no undiscovered magic in superconductors. -- Jim Pennino |
No antennae radiate all the power fed to them!
On Sunday, November 2, 2014 1:51:46 PM UTC-6, Jerry Stuckle wrote:
No, I don't think any part of the ISS is in "constant shadow". I believe it rotates as it orbits the earth, and different parts of it are in the shade at different times. I could be wrong, though - I've never been there :) Hard to say.. Some parts away from the sun may stay dark during a daylight pass, but they may be lit on other passes, depending on the direction and angles to the sun. I suspect they want to keep the solar panels towards the sun as much as possible, but the panels themselves may be steerable to some degree. I've never been there in person, but I've been there via camera on many an orbit. Watching the planet from that platform can be good wholesome entertainment for the whole family. :) The station itself does not really appear to roll at all. Or at least that can be detected on a lit pass, and using the earth as a "roll indicator" of sorts. But anyone can watch for themselves as long as they are in contact, and not on a nighttime pass. The cameras they are using don't seem to be too sensitive at night. IE: I hardly ever notice the lights below on a dark pass. Of course, they zip around the planet in about 90 minutes time.. So quite a few chances during a day to see what parts of the station are lit, and which are not. Some cameras, like the one I'm watching right now do not show the station at all, while the one they were using a few minutes ago did. At this moment they are fixing to pass into darkness over the Atlantic. http://eol.jsc.nasa.gov/HDEV/ http://www.ustream.tv/channel/iss-hdev-payload |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
rickman wrote in :
Sort of like wrestling a pig. You get all dirty and the pig enjoys it. That's the one I was trying to remember last week. :) |
No antennae radiate all the power fed to them!
|
No antennae radiate all the power fed to them!
On 11/2/2014 5:45 AM, Lostgallifreyan wrote:
rickman wrote in : I believe there are rather cold temperatures in space. A superconducting antenna could be used there with *no* supporting "apparatus". There's still such a thing as radiation resistance, I think, so it wouldn't stay cold even there. Given the size of a body, there's a limit to how fast it can get rid of heat at a given temperature.. I don't know the proper terminology for it though. Anyway, at low tenperature, the rate it can radiate heat is low, so it will quickly warm up out of low-temp superconducting state. Lol, radiation resistance is from the signal energy *leaving* the antenna. It does not show up as heat! You need to read up on the temperatures involved. Space is near absolute zero. The Sun warms things in the solar system, but before reaching Uranus even that heat drops to the point of N2 liquifying, 77 °K, still more than 70 °K above the temperature of space. So heat can still leave liquid nitrogen easily and allow it to freeze at 63 °K at one atmosphere. -- Rick |
No antennae radiate all the power fed to them!
|
No antennae radiate all the power fed to them!
rickman wrote in :
You are aware that a standing wave still moves up and down, no? So a trough turns into a crest and vice versa. I've seen waves on water in a tank that don;t. You can see them in the laminar flow froma tap set low, as the stream hits the ceramic. Totally static... About the other thing, I put it badly, but imaguine a tank brim-full. Now imagine a static half-wave, convex, supported by the sides with walls extended up from the tank (I didn't mention that before, stupidly). Now I'm not even sure that ONE halfwave can be static, convex, maybe it can only be stable concave due to gravity. I really don't know. I was just thining that if statiuc convex IS possible, then once set up, the edns of the takk have water reaching them below the brim, ergo you could chuck a bit more water in to top it up. :) Hence storage. Same (likely dubuious) logic as a flyhweel, in that to store extra anagery you can either rasie speed for fixed mass, or raise mass for fixed speed. If it's recirpocal, then an ability to add mass to that tank seemed to indicate storage capability being raised. There may well be a flaw in all that, but I'm expressing it as best I can. |
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