Circuit only works while touching the ground
The signal you collect with &quot;ant&quot; comes from AC wires through the capacitance between AC wires and &quot;ant&quot;. To get some input current the GND should be at least capacitively connected to the earth of the mains AC system. That's seemingly already said by others one minute earlier.
Making the circuit slower by increasing capacitance C7 can make it deaf for phones, wifi, radio stations nearby and other unwanted higher frequency signals. I would place a RC lowpass filter to the input to have full control. The circuit can even be an oscillator due capacitive feedback from output to &quot;ant&quot; or due coupling via power supply if it has not narrow enough frequency range.
Multistage high gain amplifiers often have RC lowpass filters in the line which feeds +supply voltage to the preamp to prevent the feedback through common power rail. At least a short wire decoupling capacitor should be connected between +Vcc and GND as near the transistors as possible.