On Apr 23, 9:01*pm, "Joel Koltner"
wrote:
Are there some vendors of readily available (stock) inductors that have
reasonably good Q's (100) throughout the HF band?

I'm familiar with something like the Coilcraft "maxi springs"
(http://coilcraft.com/maxi.cfm), and while they hit Q's of 100 by 30MHz, I'd
really like something that's already there by 3MHz or less (...and still have
a self-resonant frequency of 30MHz). *This seems quite doable simply by
making a larger coil with thicker wire, I'd just like to find a place that
offers such inductors off-the-shelf rather than having to wind my own.
Inductance in the ballpark of 1-10uH would be good, although it's not
critical.

The goal here is to try out making some adjustable notch filters for a
receiver (by switching L's and C's in and out, like antenna tuners do).
Hence, high Q is important, but power handling capability isn't so much, and
anything smaller than a breadbox is fine size-wise.

I usually design my filters to work reasonably well with lowish Q
inductors, say 100, so that I don't have to ever worry about the
actual Q. My rough measurements is that a Q of 100 is reasonably
reached using ferrite toroids not too far off from their optimal
frequencies etc. But some have done very good measurements of many
different coil types in search of extremely high Q inductors, the best
writeup I know is at:

http://w7zoi.net/coilq.pdf

His conclusion was that Q's of 300's over an octave or two on ferrite
cores are very practical.

Other experiments and measurements he does go through Litz wire, Litz
rope, spider coils, etc. achieving some spectacularly high Q's.

I don't think any of this helps your "off the shelf" requirement, but
ferrite cores work well within their frequency range.

Tim N3QE