A MOSFET is used as a wideband buffer amplifier. T1 is wound on a toroid of approximately /f diameter, with material suitable for frequency (usually 1- to 20-MHz range). The turns ratio should be about 4:1 depending on load impedance. Typically, at 4 MHz, there are 18 turns on the primary,
4 turns on the secondary, and the stage gain is about 14-dB voltage (ZL - 50 ).