[Top] [All Lists]

[RFI] Another source containing PWM

To: rfi@contesting.com
Subject: [RFI] Another source containing PWM
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Fri, 21 Apr 2017 00:34:29 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
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.


Roger (K8RI)

This email has been checked for viruses by Avast antivirus software.

RFI mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • [RFI] Another source containing PWM, Roger (K8RI) <=