8W Broadband FM Radio Frequency Amplifier

8W Wideband FM Radio Frequency Amplifier

This is an 8W broadband FM RF amplifier using the 2SC1971 VHF power transistor. The RF amplifier PCB layout employs microstrip line technology and is designed for 88-108 MHz broadband FM transmitters. This 8W RF amplifier circuit provides a suitable power boost for transmitters with an input power of 500 mW.

RF amplifier PCB

The PCB has a profile of 77 x 56 mm and uses FR-4 double-sided photoresist epoxy PCB material for best results.

[RF Amplifier 2SC1971 Silkscreen Layer] [RF Amplifier 2SC1971 Component Layout] [RF Amplifier 2SC1971 PCB]

RF amplifier construction

All SMD components are of type 1206. The bottom layer (ground layer) is connected to the top layer of the PCB at multiple points (through vias).

Notice:

CuL = magnetic wire, enameled copper wire

- 1 mm is approximately equal to #18 US gauge wire.

- 0.8 mm is approximately equal to #20 US gauge wire.

- 0.3 mm is approximately equal to #28 US gauge wire.

All diameters are measured from inside the coil, i.e., the 'inner diameter'.

Ensure the RF transistor is mounted on a suitable heatsink and apply some thermal paste between the transistor flange and the heatsink! (The heatsink's thermal resistance should be at least 6°C/W.)

All components are soldered directly onto the top layer of the PCB.