> N3OX wrote: I mean a real physical *measurement* not the model.<
I did just that years ago at my previous QTH. Here's the bench setup I used:http://www.w5dxp.com/coiltest.gif
The results were posted years ago and are enumerated in a lab book that's still in a box somewhere but they were consistent with an ~33 degree delay through the coil at 4 MHz.
Perhaps an easier example would be better, one that doesn't involve a coil. Set up a 10m dipole and install two current pickups, one 1/3 of the distance from the feedpoint and the other 2/3 of the distance from the feedpoint. One would logically assume that one can measure a 30 degree phase shift between those two points. However, the current phase shift is negligible, in the ballpark of one degree. Question is: How can 30 degrees of wire cause one degree of phase shift in the total current?
The answer is that one is measuring the total current on a standing-wave antenna whose primary equation is:
Itot = Imax*cos(kx)*cos(wt) current anywhere along x
Ifp = Imax*cos(wt) feedpoint current at x=0
The phase of the total current anywhere along the line (compared to the phase of the feedpoint current) doesn't change appreciably. This is the basic measurement mistake that most experimenters have made.
Now replace the 30 degrees of wire with an inductor. If one cannot measure the phase shift through a wire, why would one expect a phase shift through a coil?
Since a zero phase shift reinforces the preconceived presumed notions of a lumped inductor, almost nobody questions the validity of the results.
> N3OX wrote: This makes me wonder, do you own a hamstick? It'd be interesting to run a 40m or 80m hamstick through the Hamwaves calculator and see how long it is in modal wavelengths :-) This information really has some weird consequences for the "wind some wire on a stick" style of helical antenna building and resonating that some people seem to be fond of. <
In Dr. Corum's paper is a test to verify that a coil meets the requirements for the Corum approximations. I will run a hamstick coil through that test to see if Corum's approximations apply. I can get the number of turns per inch from my 17m hamstick loading coil.
73, Cecil, w5dxp.com