Hi Ludwig
FYI the toroids in QMX are purchased directly from micrometals in California, US (), in large quantities (10,000 or 20,000 etc). I have no reason to suspect they aren't the very best quality and with correctly specified AL values. If anyone feels the AL values are wrong then I'd be more inclined to suspect the experimental setup and/or measurement accuracy or some similar factor.
But it's tempting to overthink the inductance situation.?
Simulation is a good guide. Or calculation based on theory. In the real world there are frequently many other factors not accounted for theoretically. Results usually differ between practical measurement and theoretical prediction, sometimes only by a little, sometimes by a lot. Bear in mind measurement is subject to errors also.?
In all my work, if I use simulation or calculation, I consider that a first guide only. Then build and test. Then tweak things, see if improvement can be found. If the practical number of inductor turns differs from the theory, it doesn't upset me.?
The number of turns in the manuals are what we have found, experimentally, works best (for example with LPFs, power output and PA efficiency, as well as harmonic levels). Even so, there will always be some variation from builder to builder.?
The manual number of turns are my recommendation; most people can count, but most people don't have an inductance meter (let alone an accurate one at such small inductance values used in HF LPFs).
Having said all that... If you are confident of the accuracy of your inductance measurement for such low values, and if you wish to build it according to theory, I don't see any problem with that... And even better if you report back on your results, it will be interesting.?
73 Hans G0UPL
