On Thursday, March 31, 2016 08:20:19 AM Bruce Griffiths wrote: > The first inductor self resonance is much lower than it need be. EPCOS have > a range of inductors which have a much higher first self resonance > frequency. > > The other problem is that inductors have several resonances alternating > between parallel and series resonance. In short, your inductor model is > inadequate and gives false predictions. You actually need to measure the > filter response. > > Conical inductors are available that are effectively resonance free to 40GHz > but the largest value is around 10uH. In principle one could wind one's own > conical inductor with a larger value, However an iron powder (carbonyl iron > - available from Ukraine at least via ebay) and epoxy mixture
filling/core is required. > A cone angle of about 15 degrees appears to be suitable. > > Failing that, the classical method is to use a series string of inductors of > increasing value. Even then the various resonances need to be damped. Lossy > Ferrites and resistors can be useful, however one has to be careful not to > increase the noise at frequencies of interest. > > Bruce > Note correction above. Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
