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433 Receiver shielding
#1
My goal was to shield the "approved" receiver from any noise by putting it in an faraday cage ( alufoil box ) together with an TS-33C temp/hum sensor to record raw data because i would like to have this protocol implemented in pilight.

I was not succesful - the USB and data cable picked enough 433 signals from outside the Alubox to make this a failure.

It got even worse when i put the Pi with an powerbank also inside that box and let only the LAN CAT6 cable run out. Grounding the Alushield made no difference and even a 433remote control signal from outside could be recognised correctly inside the box ( so not all false noise )

so what are my conclusions

1 the receiver IS sensitive even without an antenna connected
2 the receiver near the pi is not a good idea because of much noise of the pi
3 a LAN cable can cause the shielding to be penetrated by 433MHz signals


has anybody a concept of a shielded connection between receiver and the pi?
 
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#2
It is a difficult issue. The main problem is that most 433 MHz devices us OOK (On-Off-Keying), it is not a mudulated RF carrier but the RF carrier is turned ON/OFF, this creates a wide spectrum of frequencies, and virtually any filter approach te regenerate the original information will fail.

(06-18-2016, 03:46 PM)satsatt Wrote: My goal was to shield the "approved" receiver from any noise by putting it in an faraday cage ( alufoil box ) together with an TS-33C temp/hum sensor to record raw data because i would like to have this protocol implemented in pilight.
In principle a valid approach, but in particular any copper cable penetrating the alu foil needs to be shielded

(06-18-2016, 03:46 PM)satsatt Wrote: I was not succesful - the USB and data cable picked enough 433 signals from outside the Alubox to make this a failure.
You do need to run the cable trough a ferrite-core coild to block the hgih frequencies.

(06-18-2016, 03:46 PM)satsatt Wrote: It got even worse when i put the Pi with an powerbank also inside that box and let only the LAN CAT6 cable run out. Grounding the Alushield made no difference and even a 433remote control signal from outside could be recognised correctly inside the box ( so not all false noise )
You do need to add blocking condensators to the power line (tantaluum for each board, ceramic for each chip)
(06-18-2016, 03:46 PM)satsatt Wrote: so what are my conclusions

1 the receiver IS sensitive even without an antenna connected
2 the receiver near the pi is not a good idea because of much noise of the pi
3 a LAN cable can cause the shielding to be penetrated by 433MHz signals
One of the main problems is that access to the AGC logic of the receiver is typically not possible.

(06-18-2016, 03:46 PM)satsatt Wrote: has anybody a concept of a shielded connection between receiver and the pi?
One power supply
One common ground for the analog part
Another one for the digital part.
All power cable in star configuration and tantaluum/deramic condensators added.
Digital and analog components separated as far as possible
 
Reply
#3
hi everyone...i am a new user here and as per my experience the main problem is that most 433 MHz devices us OOK (On-Off-Keying), it is not a mudulated RF carrier but the RF carrier is turned ON/OFF, this creates a wide spectrum of frequencies, and virtually any filter approach te regenerate the original information will fail.

circuit card assembly
 
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