145ft of RG-6 will give you over 15dB loss which is roughly 93% of the signal and that’s not taking into account the impedance mismatch. There’s little point in putting an amplifier at the bottom end of that length of cable because the signal to noise ratio will be awful.
LMR-400 will be a better option but you’ll still be losing over 75% of the signal.
Is there any way you can mount the receiver and the Pi closer to the aerial, run a length of network cable to it and power it using PoE?