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PC interference
https://www.hamradiodeals.co.uk/forums/viewtopic.php?f=66&t=99037
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Author:  G4WIM [ Tue Nov 06, 2018 7:05 pm ]
Post subject:  PC interference

I thought I'd have a blitz on tracking down some interference in the 2 meter band as I had a S5 noise across most of the band.

First guess was the shack SDR server PC and indeed it was !!

However on further investigation I discovered it was the GPU card - a GT750.

Removing this card and using the built in Intel HD GPU fixed the problem - no more nasty noises !

Makes me wonder if other GPU cards are just as noisy ?

It was noisy even with no video cable attached to it and the noise seemed to be coming from the 12V power feed.

Author:  gm7vsb [ Tue Nov 06, 2018 9:23 pm ]
Post subject:  Re: PC interference

More likely the PSU, than the GFX card itself, they do draw quite a chunk of power and if the PSU isn't up to the job then it'll get stressed and noisy.

Author:  G4WIM [ Wed Nov 07, 2018 8:48 pm ]
Post subject:  Re: PC interference

I thought that myself - but discarded it as the source for two reasons

1. The PSU is overkill wattage wise
2. Tried a different GFX card which didn't use a 12V power feed and still got the problem.

Just tried another GFX (again made by NVIDIA) and same broad band noise.

Just seems to be this one PC causing a problem - I have three other PCs in the shack, but only this one is noisy.

On reflection I think I'll try switching out the PSU just to be sure.

73 Tim

Author:  gm7vsb [ Wed Nov 07, 2018 11:27 pm ]
Post subject:  Re: PC interference

Tim,
It could be the voltage regulators on the Motherboard and nothing to do with the gfx cards at all.

Maybe try underclocking it?

Author:  G4WIM [ Thu Nov 08, 2018 8:33 pm ]
Post subject:  Re: PC interference

It could be the motherboard as it's a new design an Asus H370 supporting an i7 8700 at 3.6GHz with 6 cores - quite the beast so could easily underclock and still have CPU cycles to spare.

However running the on board graphics adapter seems to fixed the problem but from an academic aspect it'd be interesting to get to the root cause.

73 Tim

Author:  gm7vsb [ Thu Nov 08, 2018 11:33 pm ]
Post subject:  Re: PC interference

That's a nice processor and motherboard combo, shouldn't anticipate any trouble with an ASUS board I've used them for years. Currently on an X299 with an i9@4.4GHz.

If you can swap out the PSU easily, then that'll be a good starting point.

KustomPC's (www.kustompcs.co.uk) always do a great deal on parts, and they'll recomend a suitable PSU without trying to rob all your pocket money.

Author:  M6JNA [ Sat Apr 27, 2019 2:12 pm ]
Post subject:  Re: PC interference

I have been plagued by problems caused by PC's in the household but my issues are mainly in the HF bands, especially on 160 & 80m.

I recently replaced my PC Power supply for a Corsair HX Series HX750 750 W Plus Platinum, thinking it was the power supply and problem persists. I tried running the PC with no graphics card and still no good. I lowered the clock frequency in the bios and that has shifted the interfering signal up the band slightly. This now leads me to believe it is the motherboard that is at fault. The motherboard is a Asrock Fatality X99M Killer, CPU is a watercooled i7 5930k Haswell.

Any idea what I would be looking for in terms of motherboard/surface components to cure the issue?

Neil

Author:  G4WIM [ Mon Apr 29, 2019 7:27 pm ]
Post subject:  Re: PC interference

Hi Neil

I have practically the same PC in the shack and found that the USB leads were prone to radiating - so I choked them off with some clip on ferrites.

I should point out the case is metal and screens the PC pretty well.

I'd suggest you start with just AC applied and PC running but nothing else attached and see if it still generates noise. If so you've got likely got a poorly screened case and or noisy PSU.

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