On 12/23/19 10:17 AM, Taka Kamiya via time-nuts wrote:
I think the conversation is going into an area way beyond my initial intent.
My goal is to have a "good enough" source for 24V to run multiple time sources.
Yesterday, I measured the output of switcher I've been using for testing purpose only.
Holy cow it's dirty! 120mV peak-to-peak wide band noise. Put one ferrite bead on plus
side and it had an amazing result. Broadband noise disappearance and periodic pulse
(still 120mV p-p)
My goal is to have about 5mV p-p or lower capable of delivering 20Amp in
switching arrangement. It's easy to do with linear regulators but it makes the
room awfully warm. Why 5mV? Because it is good enough. If more is necessary,
it will have to be dealt with locally inside the time source itself. Cabling
can pick up that much easily.
Check out Jim Brown K9YC's compendia of filters - he's done measurements
on a variety of ferrite mixes in a variety of configurations (number of
turns, number of cores, etc.)
http://audiosystemsgroup.com/RFI-Ham.pdf
http://k9yc.com/2018Cookbook.pdf
He's done a lot of work to take the raw material data sheets and turn it
into practical recipes.
Of course, you could get yourself a copy of Snelling's book on "Soft
ferrites: properties and applications" which is the recognized tome on this.
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