RPi radiated noise on 144MHz
Posted: Sat Jul 03, 2021 11:00 am
This has been discussed on air but not sure there is a forum topic running on it.
Now we are running the Langstone NB transceiver several of us are finding the RPi radiates 59+ noise on 2 metres. Presumably, this was not so noticeable with DATV receivers but must be affecting receive performance particularly on 146.5 but also possibly 50 and 70MHz.
So what can be done about it?
My simple investigations show the radiation is coming from a number of places but the display and possibly the ribbon cable driving it are very noisy, particularly on the Portsdown home screen which has some very bright areas - you can hear the noise change between screens on top of the background hash.
I found earthing the RPi4 USB connectors also reduces it but leads and the metal heatsink still radiate.
I have managed to take the noise from one system, which is built into a metal 19" enclosure, down to a manageable level but my microwave transverter driver system which has the RPi mounted on the back of the screen in a plastic housing - the one with the camera mounted the wrong way - is still very noisy. It closes the squelch on a noise free talkback FM signal on 144.750!
Other than putting it all in a metal box, I wonder if coating everything in aluminium coated sticky tape (£7 from Screwfix and designed for heating ducts) might help although there may not be a common earth.
And I have proven most of the noise comes from the RPi and screen and not ebay switched regulators!
Any other ideas?
73
Noel - G8GTZ
Now we are running the Langstone NB transceiver several of us are finding the RPi radiates 59+ noise on 2 metres. Presumably, this was not so noticeable with DATV receivers but must be affecting receive performance particularly on 146.5 but also possibly 50 and 70MHz.
So what can be done about it?
My simple investigations show the radiation is coming from a number of places but the display and possibly the ribbon cable driving it are very noisy, particularly on the Portsdown home screen which has some very bright areas - you can hear the noise change between screens on top of the background hash.
I found earthing the RPi4 USB connectors also reduces it but leads and the metal heatsink still radiate.
I have managed to take the noise from one system, which is built into a metal 19" enclosure, down to a manageable level but my microwave transverter driver system which has the RPi mounted on the back of the screen in a plastic housing - the one with the camera mounted the wrong way - is still very noisy. It closes the squelch on a noise free talkback FM signal on 144.750!
Other than putting it all in a metal box, I wonder if coating everything in aluminium coated sticky tape (£7 from Screwfix and designed for heating ducts) might help although there may not be a common earth.
And I have proven most of the noise comes from the RPi and screen and not ebay switched regulators!
Any other ideas?
73
Noel - G8GTZ