At 12:21 PM 12/27/03 -0500, Tom Rauch wrote:
I generally build my own because the commercial filters I find either have
output and input bypass capacitors to common grounds [A] making them poor or
useless for common mode rejection or they have bifilar windings with poor or
NO shunt caps between the lines [B] making them poor at differential mode
rejection.
I would infer from this that if you knew what was inside the boxes, it
might be possible to build a fairly decent filter by putting one of type A
and one of type B in series. Is that correct?
Alternatively, I see on page 1077 of the current Mouser catalogue that
Schurter appears to make some 1 and 2 stage filters that do this all in one
package. Do any of those meet your specs for HF rejection? There are a
number of others on the facing page by Schaffner that make claims to high
differential and common mode rejection, but no circuit diagrams are
included. Looking at the data online, they appear to be similar to the
Schurter units, and claim quite high rejection for both common and
differential modes in the HF range (assuming I am reading the curves
correctly, which is not at all certain).
See
http://www3.schaffner.com/components/emc_filters/_pdf/single-phase/ds_FN_332.pdf.
73, Pete N4ZR
Happy Holidays
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