Reg Edwards wrote:
See program SOLNOID3 which calculates inductance of 1-turn loops, via
multi-turn solenoids, to straight wires.

Reg, at http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43)
gives the helical wave guide effective characteristic impedance.
Unfortunately, that web site is not responding at the moment (probably
because all the gurus here are accessing it wondering what they did
wrong.) :-) But, when the page becomes available would you take a look
at that equation? It goes something like this:

Zc = 60/Vf[I0(tau*alpha)*K0(tau*alpha)]

Is tau the transmission coefficient and alpha the attenuation constant?
Are I0 and K0 functions? Have you ever seen this equation before?

Also, Fig. 1 is a graph of velocity factor vs the diameter of the helix
divided by the wavelength for 10k, 5k, 2.5k, 1k, 500, 250, 100, and 50
turns per wavelength. It says: "Tightly wound coils are slow wave
structures." My 75m bugcatcher coil appears to fall nicely into the
catagory of a "tightly wound slow wave structure".
--
73, Cecil http://www.qsl.net/w5dxp