Help required with interference from PC

Noise and interference issues?
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simbeav
Posts: 297
Joined: 14 Oct 2014 15:00

Help required with interference from PC

Post by simbeav » 26 Feb 2015 14:16

I've just had to replace my PC and after finally sorting out (most) of the problems reinstalling SDRs and associated software, I have finally got around to actually listening and am horrified to find the the new PC is the worst source of noise that I have ever encountered (even in my QRM infested corner of the woods) !

Noise levels are up on MW and there are a few birdies and just above MW there is a large amount of noise. I'm sure most bands are affected, but the absolute worst is 29 MHz and above where I am getting bands of QRM about 20khz wide every 85 kHz or so. My previous computer gave some very narrow noise at these frequencies, but this is horrendous.

I'm presuming it is the power supply, but wonder if anybody can give some advice with the following.

1. How do I make sure it is the power supply (I suppose it could be the Sound Card / Video Card / CPU(?) or whatever). I know it is the PC as I plugged the Perseus into an old laptop and the QRM came and went by turning the PC on and off. I was going to try the power supply from my old PC, but the new one has an 8 pin connector on the smaller connection to the motherboard, the old has 6. It would be a pain after spending far too much on a PC to replace the Power supply and find it wasn't the cause.

2. If it is the power supply (or some other component of the PC) is there anything I can do ? All the articles on line leave me baffled with lots of technical information about what the cause may be, but no solution - I've always found the ferrite core solutions useless in the past.

3. If I do decide to replace the power supply, does anybody know of one (I need 650w or more for this PC) that is not too radio unfriendly - again buying a new one to find it no better, would be the final straw.

Thanks

Simon

satnipper
Posts: 752
Joined: 03 Oct 2014 12:58
Location: Western Europe

Re: Help required with interference from PC

Post by satnipper » 26 Feb 2015 16:16

A few more details would be good! What brand of PC is it? Where did you buy it? How much was it? What the CPU/Sound card/video card/monitor? What is the existing power supply? What is its power rating?

It probably is the power supply causing the QRM but simply unplug the sound card and boot up. Then unplug the the video card and boot. Noise still there? Probably the cheap Chinese made PS. Sometimes the crap is conducted into the mains and plugging the PC into an filter socket will work. I have an old Radio Shack one which worke dwell when I had a power supply replaced in an old PC and that was cheap noisy crap. I binned it in the end.

A quote from a Google:

"First, always buy a power supply from a reputable manufacturer, and look for reviews of it before you buy. Avoid cheap, generic power supplies, which tend to be substandard. Look for reputable brands that offer solid warranties and support. Corsair, Seasonic, and Antec are three manufacturers with reputations for producing high-quality power supplies, though even they may offer a few duds among all the studs. Do your homework!"

You probably won't go wrong with a 650W+ Antec but it's a PITA to retro-fit a PS. I outsourced it when I had to do one.

PCs are getting cheaper and they are getting cheaper because cheaper components are being used and manufacturers are skimping on shielding etc. This is especially true for consumer units. My new PC purchased tail end of last year is a business orientated unit (see previous posts), cost a couple of monkeys but has metal case and is very quiet both acoustically and RF-wise. I paid the dough because radio-use and SDRs were key use cases for the new machine.

regards

Stuart

satnipper
Posts: 752
Joined: 03 Oct 2014 12:58
Location: Western Europe

Re: Help required with interference from PC

Post by satnipper » 26 Feb 2015 16:17

Interesting - I wrote C-R-A-P and I see excreta.........

simbeav
Posts: 297
Joined: 14 Oct 2014 15:00

Re: Help required with interference from PC

Post by simbeav » 26 Feb 2015 21:08

Thanks for taking the time to reply Stuart.

You are only highlighting the problem I have if I decide to replace the power supply. The quote you give is fine if I am looking for a power supply which will fulfil the requirements of the usual PC user:-reliability, achieving specification and probably acoustic quietness, but absence from radio noise is never something tested in reviews.

I'm surprised that with the number of SDR users and radio enthusiasts using computers in general that there is little information about the best PSU to use.

The Novatech PSU that I have has some good reviews on the net, presumably because it achieves the requirements of a gamer or whatever and is incredibly quiet acoustically, but it is clearly excreta for my purposes.

Have you any idea what PSU is in your machine and whether it is intrinsically quiet or just made so by the shielding of the expensive case ?

Simon

daveB
Posts: 981
Joined: 07 Oct 2014 16:49

Re: Help required with interference from PC

Post by daveB » 27 Feb 2015 19:22

Then I must count myself lucky that I don't appear to have any interference from my new desktop - for which I was pleasantly surprised. It is a mainstream PackardBell product for the mass market - but it is in a metal case.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

Andrew Webster,Wigan
Posts: 1838
Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
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Re: Help required with interference from PC

Post by Andrew Webster,Wigan » 03 Mar 2015 21:22

A word of warning on Corsair PSU's they were a reputable make until they started putting Capxon Capacitors in their PSU's the worst make of capacitors on the planet.
You just don't want to risk loosing a PC due a bad PSU fortunately Seasonic and Antec are ok .

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

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