Boost a weak AM transmitter
The antenna needs a live wire and a ground wire. Try grounding the battery negative, or the earth of the oscillator. Either connect it to a water main or window frame or something, or just use another equal length of wire, laid out in the opposite direction.

Use of this circuit to transmit without a license is might break the law, depending on where you are. 

It is also likely that the crystal oscillator is radiating at 3 MHz, 5 MHz, 7 MHz, etc, and probably more effectively than it radiates at 1 MHz, which isn't so nice. Keep the antenna short, and turn the circuit off when you've finished the experiment!