I agree with teleview's assessment, there's plenty of signal power in the air. Add to that, the passive gain provided by the antenna provides nearly as much gain as an active amplifier. If you like, you can run the calculations based on the predicted NM on your TVFR. You'll find plenty of signal to spare until you start trying for reception of distant out-of-market signals. (An amplifier gives gain, but at the cost of added noise and distortion. Antenna gain does not add noise or distortion, as a plus it tends to block some interference.)
http://forum.tvfool.com/showthread.php?t=109
And in the end, if you did prove the need, you can add an amp later.