Q-factor is pretty simple to calculate:
Q = Fc / BW
where
Fc is the center frequency
BW is bandwidth of the circuit
You can measure antenna bandwidth by it's VSWR level with using threshold VSWR = (3 + sqrt(5)) / 2 = 2.618...
For example, if your antenna works at Fc=14 MHz and has VSWR below 2.618 within bandwidth BW=1 MHz, it means that your antenna has:
Q = 14 / 1 = 14.0
