jeff millar wrote:
>
> Quiet? Not the FCC Class B telecom units I've been playing with. These
> beasts put out relatively low noise differentially between output V and its
> ground but put out a lot of noise "common mode" between the output pair and
> the case (green wire ground), between the input leads and case, and between
> the input return and output return.
>
> I've been measuring these things at work and currently see 2V peak to peak
> impulses at the 75 KHz switching frequency followed by 10-20 cycle of
> ringing at about 50-100 MHz.
>
> >From what I can tell, the manufacturers pass FCC EMI testing by putting a
> resistive load on the outputs that's not connected to anything, just
> resistors floating in air. This minimizes the tendancy for the output
> ground noise to pump back into the input lines. But once we connect the
> outputs to our equipment (and it's chassis ground), the input conducted
> noise rises by 20-30 dB and we that far out of spec.
>
> jeff, wa1hco
Hi Jeff.
I had the same experience buying a CE certified supply.
Compliance emissions testing must have been done without any wire
attached to the output leads! As soon a a wire was applied , it sang
like a bird.
How did thet expect you to draw power without wire?
---
Ron
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