PC (laptop) power induces significant noise

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DerekR
Posts: 2
Joined: Thu Mar 10, 2016 12:56 pm

PC (laptop) power induces significant noise

Postby DerekR » Thu Mar 10, 2016 1:45 pm

I purchased the SDRplay two days ago, and am using it with SDR console on a new HP I5 laptop. For now the antenna is simply 50ft of hook-up wire strung out the window. I am delighted with it so far. However, I find that whenever I unplug the power supply (so it is running on battery) the noise floor drops by more than 20 dB, and the HF device performance becomes "alive".

Is this a problem with the lack of ferrite beads on the USB cable, or the lack of coax feed to the antenna, or possibly a noisy power supply? Any suggestions?

Thanks,
Derek
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WhoaNellie
Posts: 18
Joined: Thu Oct 22, 2015 12:37 pm

Re: PC (laptop) power induces significant noise

Postby WhoaNellie » Thu Mar 10, 2016 3:36 pm

I think you're already on the right track - it could be any combination of the three, or all of them. Trying to isolate them one at a time is about all you can do.

If you have a small portable radio that receives SW and/or the AM BCB, you could tune it to some frequencies of interest and move around with it to determine where the interference from the power supply is the worst and the least. By seeing how much that radio is affected with the power supply on and off you can get a good idea of how much a coax feed-in might help improve things, and you can determine how long it should be by moving around with the portable radio. Using a coax cable could be a cheap and effective solution, you just have to see.
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dlritter
Posts: 27
Joined: Fri Dec 04, 2015 7:12 pm

Re: PC (laptop) power induces significant noise

Postby dlritter » Wed Mar 16, 2016 9:25 pm

I found that the 'stock' power supply for my Gateway was very noisy. However, my IGo travel supply is quiet.
Good luck.
73
David
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K4KDR
Posts: 10
Joined: Tue Jan 19, 2016 3:26 am

Re: PC (laptop) power induces significant noise

Postby K4KDR » Thu Mar 17, 2016 1:34 pm

I noticed the same thing some time ago when unplugging the power cord from my Dell laptop.

I put a couple of snap-on ferrites on the cable between the transformer & the laptop and the noise disappeared.

-Scott, K4KDR
Montpelier, VA USA
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IZ2245SWL
Posts: 3
Joined: Wed Dec 21, 2016 7:09 pm

Re: PC (laptop) power induces significant noise

Postby IZ2245SWL » Sat Sep 02, 2017 10:58 am

The same for me with a brand new Lenovo Yoga. I have a big FT-240 31 ferrite choke with 12 turns on the usb cable added to their two ferrites built in. I made the same on the power supply cable. The floor noise improves but it is not good as the batteries one.
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