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Old 06-02-2012, 9:37 AM
kruser kruser is offline
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Join Date: Nov 2007
Location: St. Louis County, MO
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Originally Posted by 7designs View Post
FOUND IT!

Flipped the main breaker noise stopped s0 noise floor. Turned power back on and still s0 telling me it was something running that did not start back up when power came back on. Well that made me suspect my PCs. Turned my computer on and instantly s9.

So I have to PCs in the home and both cause s9 noise. But my laptops and other electronics do not cause the noise. Cable modem and wrt54g router cause no noise.

With my desktop computers off I have never seen it so quite. Many am stations coming in as I write this. Even the issue with my home theater powered sub is gone!

So, now how do I get the noise out of the PCs?

I am going to try grounding the chassis to a ground rod and see if that works. But at least I can shut them off when I want to use the radios. Thanks to all who have replied.
Good deal!

Are they home built computers? I'd see if you can borrow a power supply if they use standard ATX type supplies and start by swapping out the power supply one at a time.

Also, unplug all cables leading out of the computer including keyboards and mice and any USB devices and see if the noise is coming from an external device. I've seen some very noisy keyboards before.
I have also had some luck by grounding the chassis such as you are going to try.
Then I've had some computers that I could not shut up no matter what so I replaced them if they were something I needed to leave riunning while working with the radios.
Most times though, I was able to replace the power supplies and that would almost always cure the noise for me.

edit: I also found a lot of noise from my network cabling. It grew way worse when I switched to a 48 port gigabit switch and everything started running at gigabit speeds. I ended up buying a spool of shielded Cat6 cable and made up all new long runs and then bought shielded short cables and that cured the network noise. For me, my network noise seemed to mess with VHF low band (30 to 50 MHz) more than anything but I'm sure it could also mess with MW frequencies.
I also make sure all my computer cases are solid steel and not the kind they sell with plastic windows so you can see inside. Those cases offer basically no RF radiation protection as everything just comes right through the plastic window. It is about the same as hooking up a motherboard with all its cards and setting it on a desk with no case around it at all. You'd be amazed by all the stray RF floating around in a computer!

Last edited by kruser; 06-02-2012 at 9:46 AM..
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