Hi

I have a remote control to open/close my garage door "running" on
433MHz. Works fine from a distance of about at least 30 meters which
is fine for me.
Recently I built a system to use my smart-phone to control the garage
door. I'm using a Raspberry Pi Zero with a USB WiFi adapter. It acts
as an access point my smart-phone connects to. Works fine. But. Now, this
system somehow disturbs the original 433MHz remote control.
I have to go as close as 4-5 meters to the receiver to have it react.
I just cannot figure out how a Raspi can disturb the 433MHz
transmitter/receiver. I also tried the oldest Raspi as well as an
Olinuxino. All have the same effect.
Raspi is situated about 2 meters away from the 433Mhz receiver.
I got a Realtek RTL2838 and set up a SDR (gqrx on Linux) to see if
there is some noise coming from the Raspi on this frequency but found
nothing.
I'm out of ideas. I would be grateful for any hint.

Wielki

 

Welcome to the wonderful world of EMC. I’m guessing that the raspberry pi is not in a shielded enclosure and does not have appropriate filtering on all I/O leaving the case.....

Suggest studying EMC and look at shielding.

 

The 433 MHz is probably a sub-harmonic of one of the clocks.

 

Are you using a power supply that has proper certifications? Lots of the low-cost stuff from China is both unsafe and badly designed in terms of EMI/RFI.

 

Are you using a power supply that has proper certifications? Lots of the low-cost stuff from China is both unsafe and badly designed in terms of EMI/RFI.

Yes, I know. I was thinking it is the culprit. Tried few no change. Now Raspi is powered from the garage tor opener which provides external 24V which I convert to USB/5V.
No improvement.

 

Welcome to the wonderful world of EMC. I’m guessing that the raspberry pi is not in a shielded enclosure and does not have appropriate filtering on all I/O leaving the case.....

Suggest studying EMC and look at shielding.

Raspberry pi is in a metallic enclosure which could act as a shield, I guess I should ground it. Have to some studies as you suggest.

 

Yes shield must be grounded, otherwise it just re-emits any coupled RF.