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g86
Joined: 21 Jan 2003
Posts: 208
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Location: On top of antenna :))
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 19 Mar 2003 14:59 Wave impedance |
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How to measure practically?
  
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Hishamsaleh
Joined: 06 Jan 2003
Posts: 100
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| 19 Mar 2003 17:29 |
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| what impedance you want to mesure! media? T.L.? waveguid? what!!
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g86
Joined: 21 Jan 2003
Posts: 208
Helped: 4
Location: On top of antenna :))
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| 19 Mar 2003 18:29 |
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of free space 
| Hishamsaleh wrote: |
| what impedance you want to mesure! media? T.L.? waveguid? what!! |
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 19 Mar 2003 18:34 no past examples |
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I have never heard of a case of measuring it. All of the cases I have seen have been calculating it.
Since impedance is the ratio of electric and magntic fields, I suspect that you would have to measure these at a point. The problem being that your measurement sensor would disturb the field. (This reminds me of the atomic physics uncertainty principle.)
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loucy
Joined: 26 Aug 2001
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| 20 Mar 2003 16:33 |
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| I think this amounts to measuring the permittivity and permeability of free space. The experiments for obtaining accurately the value of epsilon_0 and mu_0 are quite complicated. I think this is the job for people in the bureau of standards. What is the purpose of looking into this?
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flatulent
Joined: 19 Jul 2002
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| 20 Mar 2003 17:26 special cases |
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| loucy wrote: |
| I think this amounts to measuring the permittivity and permeability of free space. The experiments for obtaining accurately the value of epsilon_0 and mu_0 are quite complicated. I think this is the job for people in the bureau of standards. What is the purpose of looking into this? |
For a plane wave the impedance is what you say, the fundamental electric and magnetic constants of free space. In cases where the wave is not plane, like in a waveguide or the near field of an antenna, other factors affect the impedance.
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g86
Joined: 21 Jan 2003
Posts: 208
Helped: 4
Location: On top of antenna :))
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| 21 Mar 2003 12:09 Re: no past examples |
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| flatulent wrote: |
| I have never heard of a case of measuring it. All of the cases I have seen have been calculating it. |
| flatulent wrote: |
| Since impedance is the ratio of electric and magntic fields, I suspect that you would have to measure these at a point. The problem being that your measurement sensor would disturb the field. (This reminds me of the atomic physics uncertainty principle.) |
Whenever you are measuring any energy parameter you must have to disturbe the system. It may be voltage, current or light or temperature..so you should not be worry about too much. Just think how to perform it without disturb it much.
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