LimeSDR-USB - Problem with Transmitting

Hello everyone,

I am trying to hack my remote doorbell and already successfully replayed the signal from the transmitter.
Now I am trying to jam the signal.

This is my setup in GnuRadio:

When I place the receiver on top of the LimeSDR, it works almost everytime (if the sender is some metres away). How can I achieve that the signal is jammed when the receiver is further away from the LimeSDR?

Thank you already for your answers.

Kind regards,