computer interference

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  • Updated 4 years ago
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I get strong interference across the band from my computer.  The primary peaks are about 40 KHz apart, but I get other spikes showing up on the panadaptor also.  The interference is coming from my desktop PC.  When I shut it off and use the laptop, I do not have the interference.  Some ideas on how to filter this out?
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Richard - N7HX

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Posted 4 years ago

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Duane, AC5AA

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First step is to find out if it's conducted or radiated interference (or both).  If you are running the Flex on the laptop and you turn your desktop computer on (with no physical connections to it) do you still hear the interference?  If so, how loud, by comparison?
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Richard - N7HX

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I unplugged the monitor and it made no difference in the noise level.  It must be the power supply.  The main spikes appear about every 40 kHz.  If you listen to the noise it has a low pitched drone to it with a ticking that sounds something like a clock.  It all goes away when I turn off the computer.  And I am using a Cooler Master power supply instead of the stock one that came with my Dell desktop.
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Robbie - KI4TTZ

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I posted a thread a few weeks ago with a similar problem, turned out to be the power brick connected to my monitor. I used a HT tuned to a frequency with the interference and just started pointing it around the room. Do you still have the old stock power supply you could plug in temporarily to see if the noise level changes?
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Richard - N7HX

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I'll swap the power supplies when I get a chance and see how it sounds.
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Richard - N7HX

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Well, I swapped power supplies and no change.  Everybody was saying it could be the power supply or the monitor, so I didn't check anything else.  So then I started unplugging the USB cords.  And guess what happened when I unplugged my FlexControl; the noise went away.  Since the cord on the FlexControl did not reach over to the right side of the desk since my computer was on the left side, I put a USB extension cord on it.  When I removed the extension cord and plugged the FlexControl directly into the computer, the noise went away.  Maybe a bad extension cord; if not, I'll have to learn to learn to use my left hand for the FlexControl.
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Tim - W4TME, Customer Experience Manager

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Not a "bad" USB extension cable per se, but probably one with lousy shielding.
(Edited)
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Al K0VM, Elmer

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Richard,
   the interference is likely the PC power supply although the monitor is also a candidate..  Depending on the PC it may be possible to replace the PC power supply and solve the problem..
The cheapest PC power supplies often leave out line filter components to minimize cost..

AL, K0VM
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Dave - WB5NHL

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Agreed, I have replaced a power supply and 1 monitor in my triple monitor configuration. It's unfortunate that replacements are so much of a shot in the dark. I agree that more expensive power supplies tend to be better. Try to find ones that might have Corcom filters.
Here is the Flex knowledge base on the subject
http://kc.flexradio.com/KnowledgebaseArticle50097.aspx
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Neal - K3NC, Elmer

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I would bet on it being the power supply enough to go ahead and buy a new one. Here is what I would use: http://www.neweggbusiness.com/product/product.aspx?item=9b-17-171-088
There are cheaper ones but you are experiencing one of the "benefits" of a cheap power supply!

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Richard - N7HX

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Interesting.  I replaced my stock power supply in my Dell desktop with a Cooler Master Extreme Power Plus 500W power supply because I was planning to add another video card and the card manufacturer suggested a bigger power supply than the one that came in the computer from the factory.  I never did add the video card so I did not need the bigger supply.  I think I will put the stock power supply back in to see if there is a difference.  I'll also try disconnecting the monitor first to see if it is causing the problem.
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Charlie

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This is very interesting.  I was having the same interference but thought it was outside my house.  I have a Timewave ANC-4 noise canceller and it does eliminate the problem but after checking the computers in my shack it is one of my computers that is also producing this same interference.  The computer I am using for my Flex is fine it is my other computer.  It is a Dell Inspiron 660 but it is a slim profile case and I believe the power supply is also a smaller version.  Would there be a replacement power supply that I could purchase for this type of computer that would have better RFI protections?
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Neal - K3NC, Elmer

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Charlie, is the power supply in the case or outside? I could not find a slim profile dell inspiron 660 picture, any help there?
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Charlie

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Neal:  It is an internal power supply.  The model number is Inspiron 660S. If a replacement power supply of better quality is not available for this model how about an in-line RFI suppressor? 
(Edited)
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George Molnar, KF2T, Elmer

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Another couple of hints -- make sure that all metal-to-metal contacts in the PC are really connected. Painted cases and insulation can render a metal case very RF-leaky. I used a Dremel to ensure that all mounting points, etc., are solidly bonded together.

You may also want to have your PC on a different AC circuit, and employ a line isolator on the AC cord. I like the Tripp-Lite ISOBLOX, but there are several options out there.

Finally - ferrite chokes on everything in and out of the PC. The little chokes on monitor cables are pretty useless at HF. As mentioned above, monitors are a big source of trouble. Use the waterfall display for a "record" of what happens when you turn off the display - it  might be revealing.

Good luck & 73

Geo/KF2T
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Richard Clafton W4/G7EIX, Elmer

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The Inspiron 660S uses a 'slimlineish' PSU and the model number is a 0650WP - I just replaced one for a Point of Sale Client.   Also used in the Vostro.
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Clay N9IO

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I too had a cheap "nasty" power supply.  Went to NewEgg and replaced it with a 500W Cooler Master.  Very clean now.
Clay N9IO