How many receivers and transmitters are used? I have seen some guys on the internet that mount only the transmitter on drone and other guys only the receiver and I just don't get it! Which one should be on ground and which one mounted on drone ? In order to make communication between drone and pc I could build an arduino receiver or transmitter (whatever needs to be on ground) so it receives the signal from transmitter on board ...but the signal it would get would only be for video ?? do I need different kind components?
... The basics:
The quad has a receiver (RX) on it that catches the control signals from the radio (a transmitter (TX) held in your hands) that's usually 2.4 GHz.
That RX sends those signals to the flight controller (FC) that translates them into control functions sent to the electronic speed controllers
(ESC) which throttle the motors in order to maneuver the quad according to the instructions of the signals being sent.
IF there is "feedback" used to give the pilot information about the quad such as battery condition, time flown, etc. then the RX on the quad
also acts like a TX to send that information back to the radio, which is known as telemetry.
Video is always a "one way only" scenario wherein an entirely separate transmitter (VTX) on the quad is sending a feed to another receiver
(VRX) which is usually 5.8 GHz. These are sometimes built into the radios, or into the goggles, or can be independant units that can feed the signal
to whatever you desire like a screen monitor or even your computer.
GPS is another thing altogether where an independant antenna and RX gets it's positional data from several satellites and sends that information to the FC which correspondingly make flight adjustments as needed.
There are exceptions to this because you can buy circuits boards that have many of these functions combines in them (AIO) but, for clarity's sake, I'm describing then as independent systems.
Also worth noting is that for long range systems different frequencies are used for these functions.
2.4 GHz and even more so 5.8 Ghz, being shorter in wavelength, are very reflective in nature. This means that the signal has less ability to "penetrate" obstacles and instead gets "bounced around" to make it's path. Long range systems use UHF frequencies like 900 MHz since they are better at traveling without such reflectivity. When using a lower frequency for command functions it's also advisable to use a lower frequency for the video feed too, otherwise the command/control system will exceed the video's capabilities by too far a margin. Switching the video to 2.4GHz when using UHF for control is typical.
Hope this explains better what you're dealing with in designing your project
