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On May 12, 4:49*pm, Art Unwin wrote:
On May 12, 3:16*pm, K7ITM wrote: On May 12, 12:58*pm, K7ITM wrote: ... To see what I mean, try entering D=10mm, N=10, len.=20mm, d=1mm, and check what C(L,p) is reported. *Now try changing D in 1mm increments up and down. *OK, so I don't trust the reported C(L,p) value, ... OK, it also helps to RTFM. *The text down below the inductance calculator explains about this some. *Also, I should have said that you need to set the "design frequency" to something low (e.g. 10MHz) to see the effect. *However, the text suggests that C(L,p) value would be larger than expected...and I've also seen it for some coils to be considerably smaller. *So I end up, then, not finding the lumped model including C(L,p) being very useful for the things I do, where I want a model that gives me _decent_ agreement over a broader frequency range, rather than perhaps more exact agreement over a very limited frequency range (as happens when the reported value of C(L,p) gets very large; try "design frequency" = 1MHz for that coil). Cheers, Tom Again I state. *If you are using Maxwell *equations you cannot stray from the units supplied.Hams do not follow the rules with respect to antennas so approximations are literally garranteed. Using Maxwells equations alone you have the presence of point radiation. With a single point radiation the rules of physics state that radiation limits is in the form of a sphere. If one states you cannot have a sphere of radiation they are breaking all the laws of physics and I certainly had no part in the making of the rules. Regards Art- Hide quoted text - - Show quoted text - you can have a spherically symetric static electric field as is easily shown by gauss's law. but in order to have 'radiation' (implying em wave propagating through space) you must have movement of some kind, that immediately removes the spherical symetry by creating an axis defined by the direction of movement. this is why even the theoretical infinitesimal dipole still produces a doughnut shaped field in free space. |
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