# Tag Info

13

Those equally spaced lines in the waterfall are very likely from EMI/RFI noise generated by modern electronics, often harmonics and/or intermodulation coming from DC-to-DC power converters. Could be something inside an LED light or lightbulb, USB charger, wall-wart switching power supply, computer peripheral or network hub, video monitor, solar panel, or ...

4

I notice you said 50 KILOhertz, not 50 hertz. Big difference, folks! You're picking up interference from some sort of electronic device that has a component producing a 50 kilohertz wave. Since this appears to be dead-on accurate down to a kilohertz or less, it's probably controlled by a quartz crystal. Any time a signal is produced at some frequency, there ...

3

Do the spikes still appear when you connect the RTLSDR to a laptop instead? Are they definitely caused by the Pi? I can see a few tones near 1420 MHz on my RTLSDRblog (with an antenna), they get stronger near a raspberry pi. One thing that might make the spikes smaller is to use more RF gain at the antenna, and turn down the gain on the SDR. Shielding the Pi ...

2

Simulating the circuit with 50$\Omega$ load and source impedance yields no resonant peaking behaviour. Also a filter made to pass HF might start looking funny by 100 MHz and will certainly be awful at 500 MHz. -- @tomnexus Yeah, that will definitely be a problem with this topology. If you are trying to operate >100MHz things don't look too good (...

2

I had the same problem......discovered it was my florescent house lights in which I have led replacement tubes.

2

If the suspected RFI is conducted from the Pi, then the RFI spectrum should change if you use a much longer USB cable with both ends of the cable wrapped several turns through large enough ferrite toroids. If the RFI is from switching power supply noise through the Pi, then the pattern should change if you loop the cord to the Pi several turns through a ...

1

Mine was from my ethernet router in my radio room. It didn't show up on lower bands, but started across 20 meters, and on harmonics. Unplugging the router made the problem, but I couldn't operate 20 meters as long S the router was activated.

1

At first I'd have said it's Xmas lights or a SMPSU, but then the 50Hz part got me thinking and remembered that it's more likely to be Ethernet over Power line device, they are also known as PLT's. These create RF noise of all types all over the radio spectrum either all the way through constantly, or in little blocks that come and go. Some have radio ...

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