I built a little quadcopter, and I need to transmit some data to it in a max. 4-5 meters range. The transmitter needs to transmit in a quarter of a sphere (the quadcopter will newer be "behind" the transmitter, neither under it); the quadcopter will only receive signals in half of a sphere: under and all around it's body.
I built a working communication system based on the RF modules in the picture below. But when the 4 DC motors of the quadcopter start, the electromagnetic noise blocks the communication. The motors are about 6 cm away from the receiver, which is surrounded by them.
1) each motor has a capacitor between its terminals, and I read that two additional capacitors, one from each terminal to the motor's case, would help; is that true? I also read "but only if the motor's case is well grounded" (I didn't rellay understand that, does it mean I have to connect the case direcly to ground?
2) I had a couple of cheap 433MHz transmitters/receivers around (I don't mean "transceivers": each module can do only one thing, TX or RX) and I decided to try using them. But many people says they're garbage: I don't mind if that's true in general, but is it possible to use them in my case whit a quite good reliability?
3) I had trouble understanding the antenna I should use. At this very moment I have two identical quarter wavelength straight 6mm copper wire antennas, one on the quadcopter and one on the ground. Are there best antenna types for this kind of transmission? I can have what I whant on ground, but the quadcopter needs a lightweight antenna.