design a quarter wave transformer to match a 73 ohms antenna to 300 ohms transmission line fed by a 100MHz FM radio station
Transformer impedance required: sqrt (73 x 300) 147.986 (say 148) ohms. The 1/4 wavelength in air is (75/100) 0.75 metres. You have not stated what you are using for the transformer, so you will need to allow for its velocity factor. But the transformer could be 0.75 metres of parallel rod spaced as required for the impedance. I am also assuming the antenna is balanced (sounds like a folded dipole).
