DrAzzy:
Pin13 is also the SCK pin, so when SPI is in use, it will flicker when SPI is actively transferring data, and stay on (or off depending on the SPI mode used) when not transferring data.
Ok. Thanks I forget this. I used nrf24 on atmega328 as arduino on beadboard and on arduino uno, on uno led 13 doesn't blink on atmaga328 blink, and radio communication doesn't work. Do you know why?