This fm rf power amplifier circuit is built with BLY94 transistor which delivers up to 50W at 175MHz and has a power gain of 7dB, arround 5x power amplification.
But in this schematic bly94 is working in 3 meter band, FM 88-108 MHz, so it has a higher power gain, 8dB – 6x. So if we use a good quality trimmers and coils with 7W input rf power BLY94 will deliver up to 50W rf power.
If you use it in C class dont connect R1.
The power supply must be 28V stabilized and must support a minimum 3.5A current consumption at 7W input rf power.
BLY94 RF FM amplifier components
R1 = 470 / 5W
R2 = 15
R3 = 50 … 80 / 2W ( depends on the output antenna impedance )
C1 = C2 = 10 – 60pF metallic plastic case
C3 = 2 X 56 …. 120pF in parallel
C4 = 100nF
C5 = 220pF
C6 = C7 = 10 – 80pF metallic case
C8 = 2 X 33pF in parallel
L1 = 2 turns / 1.5mm Ø / 14mm Ø
L2 = 8 turns / 0.8mm Ø / 4mm Ø
L3 = 20 turns / 0.3mm Ø / 3mm Ø ferrite
L4 = 4 turns / 2mm Ø / 14mm Ø 1mm gap
L5 = 2 – 3 turns / 2mm Ø / 14mm Ø 1mm gap depends on antenna impedance
T = BLY94
D = 1N4001, 1N4007