I'm playing around with these 433Mhz transmitter and receiver modules in combination with and Arduino Uno.
I first soldered a 17cm long helical antenna to both modules. After I while I noticed that a lot of noise is generated while both modules are working. I've identified two reasons for this:
- The antennas themselves: If I removed the antennas from the modules, there was considerably less noise.
- The Uno was connected to the USB port of the PC (I wanted to see the output in the serial console). The USB port of the computer seemed to also have an impact on the quantity of the noise.
When I removed both antennas and powered the Uno via an external power supply, no noise was present. Since I still wanted to see the output of the receiver I connected the TX and GND pin of the Uno to the PC via an FTDI cable.
My question is: Why was noise present when the Uno was connected to the PC via an A-B USB cable, but was not present when I connected the TX and GND pins of the Uno to the PC via a FTDI cable?