Just something to keep in mind
Working on the latest build, where absolutely nothing seems to fit, I
noticed on all the new variable speed fans (CPU and Cabinet) the letters
PWM. That computer has 7 fans, 4 of which are PWM. (forgot to count the
one on the 850W PS which is variable speed so it's 8 fans, 5 PWM) These
fans each use less than 5W at full speed and can be run directly off 12
VDC at full speed, so if necessary, all wires carrying PWM can be
eliminated except for the chips and traces on the motherboard.
"So Far" and I put that in quotes, I've never noticed noise from them,
but they might just be a problem in the plastic cased, consumer targeted
computers. Normally problems come in through the antenna(s), but many
pieces of ham equipment, including the newer top end rigs are connected
directly to the computers via CAT-5 networks, serial ports, and USB ports.
When I had the noise problem last year (it disappeared) everything got
into the receiver. It seemed like turning anything on and off changed
the noise. Even my true sin wave generator, 3KVA line conditioner
(Dedicated 30A circuit) appeared to be generating 20 to 40 over RFI.
The power supplies for my servers and USB drives were all generating
horrendous noise. 40 over with NO Antenna connected or interconnecting
coax connected to the receiver.
Will the general use of PWM in thousands, if not millions of computers
cause Tremendous RFI, raise the noise floor, cause intermittent
problems, or go unnoticed? Compared to variable speed furnace and air
conditioner fans, the power is minuscule, but the routes into the
station can be direct and numerous.
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