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Author Topic: Laptop PS noise  (Read 104 times)

N4UE

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Laptop PS noise
« on: November 04, 2019, 03:26:44 PM »

Hi. I have a newer laptop I just purchased from a great seller here on eHam. He specializes in refurbs and I'm VERY happy with my purchase. I have it in the shack dedicated to JUST ham programs (Win 10). It's been plugged in for a few weeks since I purchased it. Awesome.
Just yesterday, I fired up the 7300 to check WWV (10 MHz) and saw a horrible background on the screen. Since I live in a (NOW) very quiet rural area, and have not seen this before, I suspected the latest addition, the laptop's 'new external PS. It's fairly large and I 'thought' it was a linear type. Sure enough, as soon as I pulled the plug, the noise went away.

My only question is: did the laptop 'call' for charging at that moment? I haven't heard that noise before, but my operating time has been limited. Too many projects, etc.

Anyway, I put the PC's PS on a mechanical timer, so that it will only charge the PC when I'm not home.

any ideas?

ron
N4UE
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KH6AQ

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Re: Laptop PS noise
« Reply #1 on: November 04, 2019, 06:44:23 PM »

The switching power supply is always on and switching. Its dominant RF noise can be caused by capacitive coupling across the switching power supply transformer and may not change in amplitude when the load demands more power.
« Last Edit: November 04, 2019, 06:51:07 PM by KH6AQ »
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N7EKU

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Re: Laptop PS noise
« Reply #2 on: November 05, 2019, 02:03:49 AM »

Hi,

Normally original equipment laptop chargers are fairly RFI quiet, however every aftermarket one I've had were horrible.  I suspect the aftermarket ones are cheap inside and don't have any real interference reducing components used in their construction.  I doubt they are very safe either.  Look for a used OEM supply on ebay -- usually there are many listed for low prices because laptops die a lot sooner than their power supplies.

73,


Mark.
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Mark -- N7EKU/VE3
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