What happened to
- the radiation pattern of your transmit antenna
- the sensitivity pattern of your receive antenna
- the distance between receive & transmit antennas
- Losses of the ether medium
- rotational orientations of antennas and their polarizations.
Those are the ones that quickly come to mind.
There is a little more to the "Can you hear me now?" question than whats going into the antenna at the transmitter.
Look up - Transmitter-receiver link budgets and antennas and propagation as a start point to your research.