I want to make a notch filter at 1 MHz, to pull out a fundamental sine wave and leave the harmonics for THD analysis. The signal levels will be pretty high, maybe 50 mA p-p with some DC bias, so I'd rather not use ferrite cores, in case they might add distortion. (I have no idea how much distortion they might add.)
So I could wind air-core inductors. The range might be around 100 uH maybe. I could get a, say, 1" diameter coil form, maybe 0.25" high, and fill it with copper. Maybe Litz wire. This is getting old-timey.
I think some people here have been working with coils in this range. Any guess as to what sort of Q I could expect?
Would putting such a coil near a PCB ground plane much affect the L and Q?
I'll have to try it, but I may as well ask first.