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RFI with Laptop Power Supply

Dec 16th 2016, 03:00


Joined: Nov 17th 2015, 10:54
Total Topics: 0
Total Posts: 0
I have a strange problem with my Laptop power supply.

I am using a 12vdc supply with my solar system and batteries. I bought a special supply that is supposed to be RFI quite on ham bands. It was for a while.

Now when it is plugged into the laptop, when the laptop is off, I get massive RFI bands on 80m and less RFI on 40m and 20m.

When the laptop is turned on the RFI switches to birdies floating through the bands, about equal on 80, 40, and 20.

If I remove the power supply from the Solar batteries and attach a separate battery the noise disappears all together and the laptop works fine.

I bought two of these supplies, one for the car, so I hooked up the second one, which to this point I have not used, and it has the same problem and identical RFI.

I could run the laptop on a separate battery but if I connect the separate battery to my solar batteries to keep it charged I'm sure I'll get the RFI back.

It's unusual and I'm not sure how to resolve this. suggestions are highly coveted.

Jan 4th 2017, 18:12


Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

You may be getting common mode radiation off the wire connecting the laptop to the solar system supply. I'd suggest wrapping that wire through an FT-240-43 toroid 17 times to choke that off.

Zack Lau W1VT
ARRL Senior Lab Engineer

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