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

The post 70W FM amplifier appeared first on Amplifier Circuit Design.

This amplifier will pull in all distant FM stations clearly. Active FM amplifier circuit is configured as a common-emitter tuned RF pre-amplifier wired around the VHF / UHF transistor MFE201. There are several other types of transistors that will probably work as well, such as NTE107, 2SC2570, etc. but this is untested.

Adjust capacitor trimmers C1 and C2 for maximum gain. Input coil L1 is made up of 4 turns of 20SWG enamelled copper wire over the 5mm diameter former. It is tapped at the first turn from ground lead side. Coil L2 is just like L1, but has only 3 turns. Pin configuration is shown in the diagram.

The post Active FM Amplifier appeared first on Amplifier Circuit Design.