On 1/30/2014 6:41 AM, W5DXP wrote:
On Wednesday, January 29, 2014 6:20:16 PM UTC-6, amdx wrote:
This evening I'll wind a 55uH coil and find a 3,072 resistor. I'll put
these in series and see how it measures compared to my lossy ferrites
beads on a cable.

A coil of that large size will exhibit transmission line characteristics that will render the lumped-circuit model inaccurate because the current into the coil will not be equal to the current out of the coil. Better to use the distributed network model which is closer to Maxwell's equations. Here is an inductance calculator that will yield more accurate results for coils that are greater than ~15 degrees long electrically. Using the axial propagation factor (Beta) of the the coil, one can calculate how many degrees it occupies. Then using the characteristic impedance (Z0) of the coil, one can analyze the circuit like a transmission line using the distributed network model. If you will describe the characteristics of the coil in detail (total turns, length, wire size, etc.) I will do the analysis for you.
--
73, Cecil, w5dxp.com


I used an adjustable inductor I made with 7/16 polypropylene tube, wound
with 660/46 wire and a ferrite rod I slide in and out to set the
inductance. The Q was 250 at 3Mhz on my Booton 260.
Mikek