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September 2nd 03, 04:22 AM
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In article , starman
wrote: John Doty wrote: In article , wrote: So what would you think the relative 'resonant frequency' of the small diameter and shorter Slinky Jr. be ? ? ? One of the peculiar things about a small diameter helix is that over a rather wide range of pitch angles and diameters it resonates at approximately twice twice the frequency that it would if it were stretched out straight. Is there a formula that applies to a Slinky? Not hard to calculate this with a helix of at least three turns will result in an impedance of ~ 140 ohms: Wavelength = WL Diameter of a turn .35 WL Circumference of a turn 1.1 WL Pitch ~ 13.5 deg Spacing between turns WL tan 13.5 deg (about 1.35 WL) Seen from the side the helix should look like a sine wave proportional to the size of an EM wave it is made for in air. From this you can probably guess how it works. A typical slinky would work in the microwave range. I consider the helix to be a basic antenna in that it emulates the way a wave travels in space. A reference dipole is like space terminated to a passing wave. -- Telamon Ventura, California |
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