70W FM amplifier

The following circuit is a power amplifier for FM stations, this time with a power output of 70 watts.

The heart of this stage is an RF transistor (the BLY90) which, together with the classical passive components in such systems, performs the function of amplifying the radio signal present at its base to deliver to its collector.

The power supply is 14V, with a current of 7 to 8A. It is almost impossible at this stage parasitic oscillations occur. Second harmonic suppression is better than 45dB.

L1 3 Turns on air 7mm
L2 Shock of RF 0.22μH
L3 15 turns 0.5mm wire on a 47K resistor ½ W
L4 3 Turns on air 5mm
L5 Arch 25mm high by 15mm wide. 0.5mm to 5mm wire
L6 Shock RF
L7 3 Turns on air 7mm
L8 4 Turns on 8mm air