RF 433 MHz modules working randomly

I've built a project using Arduino UNO Rev 3 with RF transmitter and receiver modules. This modules are cheap ones that can be bought at sparkfun or chinese shops.

I've built a standalone circuit on a breadbord with an ATMEGA328P-PU that runs with one 9V battery. In this breadboard the transmitter module runs perfectly. But when I move all this to a stripboard the fact is that it stops runnig (the receiver doesn't get anything). I've spent weeks trying to find out the problem: the voltages at every point of the stripboard are the same than at the breadboard, and I've tested over and over that the layout is ok.

Finally, I've found that I can get the transmitter runnig if I solder it in a separated piece of board, or changing the lengths of the cables that connect it with the microcontroller. But the problem is I don't understand why this happens and I can't predict how is this circuit going to behave.

Any help will be appreciated. Sorry by my poor english (I'm spanish).

Thank you very much!

Are you using an antenna?
For some projects, I found the use of a 9V battery caused problems.
Swapping to 4 x AA batteries seemed to improve things. Not sure if this would help in your case.

I'm not using an antenna. I've seen that when I attach a cable to the antenna pin of the transmitter, it stops transmitting.

I'm using a 9V battery and a 7805 voltage regulator. The output voltage is 4'9V. So, I think that's not the problem.

Thank you very much. Any other ideas would be appreciated!