Topband: Computer noise

[YL2VW]

Hi

I suggest checking if there is good electrical contact between the metal
casing of the PC power supply unit (PSU) and the computer metal case itself
- scratch off the case painting under screws keeping both of them together
to provide better contact.
I had terrible RFI from my freshly assembled shack PC this August. And
while experimenting with extra grounding it to get rid of RFI, for my
surprise I discovered that noise goes away by ~95% when I mess with case
screws. Then I scratched the case painting off below the screws and noise
was almost gone. I assume if it would be in neighbors house, I wouldn't
feel it anymore then.
However, there still were some weak RFI birdies here and there (60 Hz
spacing approx), and as it was meant to be my HAM shack PC, I could not
live with idea that I add extra noise on top of existing neighbor's crap.
So I just replaced the PSU to another one I got for free after asking
friends around, and luckily no more RFI issues from this PC.

The RFI generating PSU was brand-new "Be Quiet! System Power 9 500W" (I
find the name ironical for a PSU generating RFI). The good one had Chieftec
label. Both of them are kind of "made in China, quality controlled in
Germany".

73!
Agris/YL2VW


On Tue, 26 Nov 2019 at 13:49, Rodman, David <rodman at buffalo.edu> wrote:

> A few ideas might be helpful here.  I was at the station over the weekend
> and found a significant amount of noise coming from one of two computers in
> the station.  Significant noise S5 at 1820.  One computer runs the cluster
> and 2m connection.  That was clean.  The other handles most of the remote
> chores and has about 15 USB serial devices attached.  Everything was off,
> except a battery operated transceiver attached to the receive antenna feed,
> the modem for the cable and my router.  One can definitely see that
> operating the computer, closing windows or plugging in USB devices causes
> the modulation on the signal to change, this isolating the source to the
> computer alone and possible connections to peripherals (they were all
> turned off by the way).  I did have few chokes available but attaching them
> to the USB wires out of the computer to their various devices made no
> improvement.  I could get more specific but need to leave for my office
> now.  Any ideas might be helpful and appreciat
>  ed.
>
>
> ---
> David J Rodman MD
> Assistant Clinical Professor
> Department of Ophthalmology
> SUNY/Buffalo
>
> Office 716-857-8654
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