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Richard Harrison wrote:
Gene, W4SZ wrote: "The current lags voltage principle does not settle anything in this case." W8JI claims that current flows into a turn at a coil end/s and is induced without delay into all turns of the coil, overcoming delay that the coil might otherwise impose. If that were true, Terman would have told us so. In fact, Terman tells us the opposite is true in explaning the traveling wave tube begining on page 678 of his 1955 opus: "The signal to be amplified is applied to the end of the helix adjacent to the electron gun. Under appropriate operating conditions an amplified signal then appears at the other end of the helix.-------inapplicable info deleted-----. The applied signal propagates around the turns of the helix and produces an electric field that is directed along the helix axis. Since the velocity with which the signal propagates along the helix wire approximates the velocity of light if the frequency is not too low (caveat is unimportant, see footnote in book), the axial field due to the signal advances with a velocity that is very closely the velocity of light multiplied by the ratio of helix pitch to helix circumference." In other words, the axial advance is much like that of a threaded bolt as the pitch angle is always fractional. Kraus details this in his section on helical antennas. Best regards, Richard Harrison, KB5WZI Richard, I would never argue with Terman. You completely changed the subject, so I have nothing further to say. The line you quoted above is still correct. Feel free to continue on in whatever new direction you want. 73, Gene W4SZ |
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