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SDRplay Notebook interference

Posted: Tue Aug 08, 2017 4:34 pm
by Phoenix
Hello,
i just received my RSP2 Pro today and i am very happy with it. It is very sensitive and it excelled my expectations. I just have one problem. My notebook seems to produce a lot of unwanted signals. I built a small adapter to connect to the High Z Port via BNC. The adapter only consists of 30cm (1 foot) RG58 Coax and a female BNC connector. As soon as is start SDRuno a lot of unwanted signals appear. My guess is that it has to do with the USB cable acting like an antenna. I am already using a high-end Usb cable with double shielding and a ferrite core. I tried a cheap USB cable and the signals got worse. Any idea how i can fix this? The signals only have a very small bandwith but they are still distracting. They do not disappear if i connect my longwire antenna to the RSP. It is not the RSPs fault because if i disconnect everything they are gone. I also confirmed the signals with my other radios.

Re: SDRplay Notebook interference

Posted: Wed Aug 09, 2017 8:31 am
by vk7jj
Try turning off the notebook's mains power supply and running it from it's internal battery, just as a test.

At the same time turn off any switch mode power supplies in the vicinity, they are notoriously bad for producing strong spurious signals.

Re: SDRplay Notebook interference

Posted: Wed Aug 09, 2017 2:59 pm
by Phoenix
vk7jj wrote:Try turning off the notebook's mains power supply and running it from it's internal battery, just as a test.

At the same time turn off any switch mode power supplies in the vicinity, they are notoriously bad for producing strong spurious signals.


I always run Sdruno without the notebook's power supply. If i run it with it the noise floor is very high. Could i run my Pc on a powerbank to fix that? Sdruno drains a lot of battery.

Re: SDRplay Notebook interference

Posted: Wed Aug 09, 2017 4:11 pm
by DanubeBCL
Have you connected the shield of the coax adapter to ground?
Try a 9/1 balun at the RSP input. Coax shield of course grounded.
In general laptop power supplies are very stubborn. They produce high noise levels and are almost impossible to de-noise. Place the antenna as far away from the laptop as possible and disconnect the power from the laptop while receiving. As VK7JJ already mentioned switched PS in the house (and the neighbourhood) are poison for reception, too. Especially the black wallmarts used for routers, IP cams a.s.o. are often noise catapults.
473, Heinrich

Re: SDRplay Notebook interference

Posted: Wed Aug 09, 2017 5:58 pm
by Phoenix
DanubeBCL wrote:Have you connected the shield of the coax adapter to ground?
Try a 9/1 balun at the RSP input. Coax shield of course grounded.
In general laptop power supplies are very stubborn. They produce high noise levels and are almost impossible to de-noise. Place the antenna as far away from the laptop as possible and disconnect the power from the laptop while receiving. As VK7JJ already mentioned switched PS in the house (and the neighbourhood) are poison for reception, too. Especially the black wallmarts used for routers, IP cams a.s.o. are often noise catapults.
473, Heinrich


Thank you very much for your help. I was only using the P and N Port of the High Z Port because i saw an article that you should only use these two if you use a balun with 50 Ohm like i do. Now i connected the shield of the coax to the GND Port. The noise is absolutely gone. No more spikes. The center conductor is now going to the P port and the shielding is going to the N and GND port.

Re: SDRplay Notebook interference

Posted: Thu Aug 10, 2017 9:39 am
by vk7jj
Well called DanubeBCL :-)

Great to see a straightforward fix, getting rid of noise and lowering the rx noise floor sometimes becomes a never ending quest.

Re: SDRplay Notebook interference

Posted: Thu Aug 10, 2017 6:01 pm
by DanubeBCL
vk7jj wrote:getting rid of noise and lowering the rx noise floor sometimes becomes a never ending quest.
That's true, Phil. As long as the noise is produced by ourselves we can do something against it. Shielding, grounding, common mode baluns, power line filters ...
But the problem worldwide is more and more that the manufactures of electric devices no longer care of de-noising. They save every coil and capacitor in their tellies, monitors, switched power supplies, lawn mowing robots, photovoltaic inverters ... And in many countries high RF noise levels are definitely allowed by law. One of the saddest examples are homeplug powerline modems (PLC) explicitely allowed with signal levels of up to 105 dbµV here in Europe. You are helpless when your neighbours have them. All totally legal, of course.
73, Heinrich