@virtualmkr Oh, man. Here in Italy too, AFAIK. So, it would be a good idea to add it? Is it really just a coiled copper wire that I can do myself?
Also, is the knob to calibrate the frequency?

@virtualmkr Thanks for your answer, but I didn't ask for help on my project, just those four questions. To summarize, what's the coil I miss for, why the different receiver name, what's the screw for and if I should ignore the antenna hole being soldered. Thanks again!

I know it's been 20 days, but I bought five, even if I still have to test them.

I just did with a simple LED blinking circuit and all went fine (a little bit of initial tinkering with the IDE is needed, but you already done that since you said you've done the blinking).

Can you post your sketch and your circuit schematic or a photo of it?

Hello everyone! I want to control an RC car using Arduino-compatible boards, so I bought some cheap 433MHz modules. However, I have some questions about it (I am not able to find a datasheet):

• My receiver is named MX-RM-5V instead of XY-MK-5V, like I read anywhere else. Since my module name gets me no result on the internet, does anyone know that and can tell me the differences, if any?
  

• All the images of the transmitter I find have a coiled copper wire I shy. Is that important? What does it do?
  
  

• The hole I should solder the antenna on the receiver is soldered shut. Should I think nothing of it and just melt the solder, attaching the antenna like if the hole was left free?
  

• What does the little knob in the green cube do in the receiver? Maybe I'm a lousy searcher, but I didn't find the datasheet, nor specific answers for that.

Thanks, a good day to you!