Hi The BLM18 gives you 300 ohms at zero current. It’s impedance at zero current per the data sheet. If you look at other parts of similar size, the impedance drops to nearly zero at the “rated current”. Great if you have a signal lead and no current. Not so great if you have an OCXO that is pulling 600 ma in a cold garage lab. A bead for close to 1A use with 100 ohms at the 100 MHz would be much larger. At the 10 MHz frequency of interest, anything close to 100 ohms would be even larger still.
Bob > On Dec 5, 2016, at 7:24 AM, Attila Kinali <[email protected]> wrote: > > On Sun, 4 Dec 2016 17:07:53 -0800 > jimlux <[email protected]> wrote: > >>> Wouldn't it be better to use a ferrite bead instead, for this application? >>> The much lower series capacitance and thus higher self-resonance frequency >>> should help damping the spurs. >>> >> sure, if you can get enough L. The other thing is that SMD inductors >> can be placed by machine, which isn't necessarily the case with ferrite >> beads (depending on how you do them). > > A BLM18 gets you into the order of 300Ω @ 100MHz, which is about > the equivalent of about 480nH. Using a lower current version gets > you into the 1kΩ @ 100MHz range (~1.6µH). Shouldn't that be enough > inductance? > > > Combined with some 10µF of capacitance and you already get ~15dB @ 1MHz > for a simple LC-lowpass. For additional filtering, add something like an > NFM18PS105 and you get good filtering up to ~100MHz. > > > Attila Kinali > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
