Indicators and characteristics of the circuit: Component List No component parameters and describe the FEC Model (Note 1) the number of C1, C2, C4 5.5 - 50p Small Ceramic fine-tuning capacitor 148-1613 C3 100p 50V Ceramic capacitor (NP0) 896-457 1 C5, C6, C7 100n 50V Ceramic Capacitor (X7R) 146-227 3 C8 100u 35V Electrolytic Capacitor 667-4191 C9 500p 500V high-frequency capacitance (metal clad Note 2) 1 Capacitor C10 1n threading 149-1501 C11 16 - 100p mica fine-tuning capacitor (Arco 424) 1 C12 25 - 150p mica fine-tuning capacitor (Arco 423 or Sprague GMA30300) 1 C13 300p 500V high-frequency capacitance (metal clad Note 2) 1 C14, C17 25p 500V high-frequency capacitance (metal clad Note 2) 2 C15, C16 50p 500V high-frequency capacitance (metal clad Note 2) 2 C18 100n 200V Ceramic Capacitor 1 L1 64nH inductor diameter 1.2mm enameled wire into the hollow coil diameter of around 6.5mm 4 turns stretched to 8mm 1 L2 25nH inductor diameter 1.2mm enameled wire into the hollow coil diameter of around 6.5mm 2 turns stretched to the length 4mm 1 L3 in the six holes with diameter of 0.7mm enameled wire on a bead around 2.5 turns 219-8501 L4 210nH inductor diameter 1.2mm enameled wire into the hollow coil diameter of around 6.5mm 8 turns around the length of 12mm 1 Mi L5 21nH inductor diameter 0.8mm enameled wire into the hollow around the diameter of 4mm 3-turn coil stretched to 10mm 1 L6 41nH inductor diameter 0.8mm enameled wire into the hollow coil diameter of around 4mm 4 turns stretched to 6mm 1 L7 C10 at the power lead on a set of two beads 242-5002 L8, L10 100nH inductor diameter 1.2mm enameled wire into the hollow coil diameter of around 6.5mm 5-turn stretched to 8mm 2 L9 115nH inductor diameter 1.2mm enameled wire into the hollow coil diameter of around 6.5mm 6-turn stretched to 12mm 1 R1 10K 0.5W adjustable resistor (potentiometer) 108-5661 R2 1.8K 0.5W Metal Film Resistors 333-8641 R3 33R 0.5W Metal Film Resistors 333-4401 D1, D2 BZX79C5V6 5.6V 400mW Zener Diode 931-7792 TR1 MRF171A (Motorola) RF Power MOSFET 1 SK1 BNC socket 583-5091 SK2 BNC or N-type sockets 310-0251 16 x 60 x 89mm 3.4 ° C / W heat sink and fan 170-0881 Note: FEC model for reference only. Metal clad high-frequency capacitance of the short and thick with a minimum lead inductance. Input circuit of the inductor coil can be smaller, but in order to make convenience, and the output circuit using the same large coil. Amplifier Photo 40W output power 88-108 MHz frequency range 20dB Gain +28 V 3A DC Power Supply High efficiency (70%, MOSFET AB class amplifiers) Less components Output low-pass filter (LPF) Assembly Preparing a 100 x 85mm double-sided printed circuit board (PCB). Drill a FETFET power tube to pass through the holes. In the 4-6 drill holes on the PCB to be shielded PCB fixed on the cast aluminum box. How to design a good device, a fixed heat sink and fan. In the cast aluminum shield box set power supply, input and output sockets needed holes. Reference to the photos and schematic in the PCB cut out the welding zone. PCB on the back and positive most of the area is ground. Welded components. Part of the output low-pass filter with copper (or the printed circuit board) and the amplifier circuit part of the shield separated. Output low-pass filter function: filter is used to filter high harmonics, and to reduce the interference caused by nearby radio station, which is important for high-power RF output. For example, suppose the third harmonic of the amplitude ratio is-30dB. When the 1W amplifier when the harmonic power is 1mW, nothing; but when the amplifier is a 40W harmonic power is 40mW, interference is a problem. The circuit harmonic suppression greater than 50dB. If you do not involve tampering with the problem, you can not output low-pass filter. Debugging Bias adjustment: Input with 50 Ohm resistor short-circuit (Note: This circuit is not the case then the input would be self-excited oscillation) will be transferred to the middle of all the variable capacitor will be transferred to R1 voltage minimum. Connected to the +28 V power supply, the current should be 14mA this time around. Adjust R1 so that power supply current of 115mA. If you find a sudden increase in current is a lot of shows that self-excited oscillation circuit requires more shielding isolation. Input and output matching adjustments: Recommended equipment: Limiting the power (+28 V, 3A) Pseudo-50W VHF antenna load 500mW-1W FM Transmitter RF 40dB attenuator RF Power Meter RF spectrum analyzer and network analyzer If you have a RF spectrum analyzer and network analyzer can be used to adjust these instruments. Without these devices it does not matter; in the input through the FM transmitter to join 500mW-1W RF signal, the output of a 50W Dummy Load Termination and, through a 40dB attenuation of a RF power meter Used for measuring output power. If you do not have RF power meter, just on the right side of the detector circuit with the measurement of the voltage monitoring points. To set the transmitting power of transmitters to regulate the fine-tuning capacitor C1, C2, C4, C11, C12, so that maximum output power amplifier.