Topband: Computer noise

[Pete]

Corcom makes a variety of filters that are designed to replace the AC power input connector on PC power supplies. I have done this on two and had good results. 

73, Pete N4ZR 

Sent from my iPhone

> On Nov 29, 2019, at 8:59 AM, YL2VW <yl2vw at lral.lv> wrote:
> 
> 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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