On 2/17/2025 5:08 PM, Joe Subich, W4TV wrote:
Having just begun a noise mitigation project, I've found
two of the biggest sources to be a pair of wall warts for
the USB hubs attached to my radio and office computers.
Removing them dropped the noise floor by 20 dB on both
160/80 (and by about 10 dB on the other bands).
Does anyone have a recommendation for a source of *quiet*
replacements (preferably with 3.5 x 1.35 mm coaxial plug)?
I fought a Sony VAIO laptop wallwart a few years back about noise.
Finally wound up building a small linear power supply with a transformer
and some regulator chip. Fortunately, that VAIO only had a two-wire
cable to the power supply (running W7, so it's almost useless these
days). A later HP laptop (running W10, so it's shortly about to also
become useless) running from the same voltage (+19.5VDC) has a
three-wire cable and although people on the web claim you can simulate
that third wire with a high-value resistor to the plus side, that hasn't
worked for my HP; so I had to do other "cures" like hide it's wallwart
inside a large metal box with a dozen beads on both the input and output
cables to quiet them down, as well as finding locations for the box
where my antlers don't detect it as easily.
That's why I usually buy up small power transformers at swap meets: for
linear supplies to replace the switchers. 5V/3A would be a snap and real
easy to make; try it!
Steve, K0XP
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