On 3/16/2019 8:40 AM, Claude Frantz wrote:
I have noticed that the display of laptops and standalone ones, the
power supply of PC's and laptops are often the source of very bad noise.
Where can we find good recommendations about which product to use or to
avoid ? There is many information available about acoustic noise of
power supplies, but nearly none about radiation and electrical noise.
Yes, I've seen this as well. I've used nothing but Thinkpads for at
least 15 years. I've heard no noise from their power supplies, but that
may be because I always wind all wiring onto ferrite cores. I have
experienced direct radiation into closely spaced antennas that
correlates to what is being displayed on the screen. This has not been
true of all models (I've owned at least six different ones over the
years) -- most have been quiet.
In general, except for truly awful devices, RF noise not radiated by
circuitry inside the device itself can be well suppressed by winding
turns of all connected cables through suitable ferrite cores to form
common mode chokes. The "truly awful" devices I have encountered have
all been switch-mode power supplies (SMPS), including those sold as
battery chargers. Most power supplies sold today are SMPS, and while
it's possible to design and build them so that they are RF-quiet, it's
cheaper not to make them quiet, so the vast majority are noisy.
73, Jim K9YC
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