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RFI from raspberry 4B

Yannig - F4IUJ All Messages By This Member #7414 Hello all, My raspberry Pi is creating so much RFI that I need to switch it off to traffic... That bugs me and I am 90% sure that the culprit is the USB bus. As you all seem to be getting on well with your Pis, I must be doing something wrong... My setup at the moment : A small 5V switch mode supply that I bought to replace the noisy and underpowered supply I had before. I initially thought that it was the culprit but no it is not as if I run it alone I am fine... The supply is directly connected to the appropriate pins of the GPIO of the Raspberry. That is still fine Now starts the weirdness... If I plug my RTL-SDR or my WIFI dongle into the raspberry USB port, I become deaf as horrendous RFI appears in the shack, it is like trying to have a conversation in a noisy night club, hopeless!!! It doesn't matter if the raspberry is switched on or off, it still happens If I use the USB 2.0 port instead of the 3.0 may be it is a little bit better but it still is terrible I am stuck, any suggestion to make some progress is welcome... 73 Yannig - F4IUJ
Ken N2VIP All Messages By This Member #7430 开云体育 With the power supply attached to the GPIO pins, your RTL SDR dongle is probably always powered on, as confirmed by the RFI being generated if the RPi itself is on or off. can you borrow a different dongle and try it - preferably from a different source/manufacturer? Can you try powering the RPi from a conventional power supply connected to the USB-C connector? Powering the RPi thru the GPIO pins should be fine, but who knows? Ken, N2VIP toggle quoted message Show quoted text On Mar 4, 2022, at 05:54, Yannig - F4IUJ via groups.io <yannig.robert@...> wrote: ?Hello all, My raspberry Pi is creating so much RFI that I need to switch it off to traffic... That bugs me and I am 90% sure that the culprit is the USB bus. As you all seem to be getting on well with your Pis, I must be doing something wrong... My setup at the moment : A small 5V switch mode supply that I bought to replace the noisy and underpowered supply I had before. I initially thought that it was the culprit but no it is not as if I run it alone I am fine... The supply is directly connected to the appropriate pins of the GPIO of the Raspberry. That is still fine Now starts the weirdness... If I plug my RTL-SDR or my WIFI dongle into the raspberry USB port, I become deaf as horrendous RFI appears in the shack, it is like trying to have a conversation in a noisy night club, hopeless!!! It doesn't matter if the raspberry is switched on or off, it still happens If I use the USB 2.0 port instead of the 3.0 may be it is a little bit better but it still is terrible I am stuck, any suggestion to make some progress is welcome... 73 Yannig - F4IUJ
Yannig - F4IUJ All Messages By This Member #7432 On Fri, Mar 4, 2022 at 04:57 PM, Ken N2VIP wrote: With the power supply attached to the GPIO pins, your RTL SDR dongle is probably always powered on, as confirmed by the RFI being generated if the RPi itself is on or off. I think you are onto something as with the RPi off but powered through the GPIO, I get noise with the SDR dongle connected but not with the WIFI dongle connected. So obviously it might well be the dongle, I will try to connect it to a laptop to see if the same issue arises. It is at the end of a long USB cable, may the USB cable is acting as an antenna ? My shack is at the top floor of a 4 storey building. I don't have a reliable RF earth up there, if I could earth the SDR dongle, may be it would be easier!!! 73, Yannig - F4IUJ
Mark - WB8SFY All Messages By This Member #7433 With the Raspberry Pi 4B? I have always used the official Pi wall wart PS.? It is recommended that 5.1 at 3A be supplied to the Pi4's USB-C port, that supply meets that criteria.? In the past they have been readily available for about $7.99.? I have not had any issues with excessive RFI.? I have seen some 5v and 12v wall warts (switching supplies) that were so noisy that I had to remove them from service and put them in the trash because they even interfered with strong local AM stations.
Mike Thompson All Messages By This Member #7434 I agree with Mark Johnson. When it comes to RFI issues with USB devices, I have had very good results using a type 31 mix ferrite and placing as many turns of the USB cable as possible through the ferrite. If you have ferrites and are unsure what type they are, they probably aren't Type 31. This is the only mis to use in ham?radio / EMI suppression. Additionally, I take a silver sharpie and mark them with a "31" so in the future, I know what type they are. You can buy them on Amazon. If you are plugging the SDR? directly into a USB port on the Pi, I suggest purchasing a shielded USB extension cable (not all are...) to plug the SDR into it and placing the Type 31 ferrite as close to the SDR as possible. ? -- Mike WB8ERJ Geeze! What is he up to now?

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