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This is an On Air indicator , ie an indicator circuit dr RF transmission , very simple and useful for those who like RF . This circuit detects the RF output using a visual indicator , but with some modifications , the LED may be replaced by a relay or any other system that want to trigger when the transmitter is switched on. The output of the transmitter or other RF generator must be connected to this RF input circuit.   Simple Circuit indication for RF Output Transmitters List of components Resistor R1 560Ω eighth Capacitor C1 330pF disc C2 Capacitor 0.1μF disc Diode D1 1N34 or 1N60 D2 LED Transistor Q1 2N3904 or equivalent  If you liked this article,Take a few Seconds to Share this and leave comments

This RF amplifier circuit diagram is a very simple and is designed to work for 10 meters band (26 ... 30 MHz) reserved for amateurs. By making this RF amplifier small power transmitters of 200 mW, can be transformed into a power transmitters reasonable, ranging between 2 and 3 W. The circuit is very simple. Network output filter suppresses noise by at least 55 dB. Simple RF Amplifier Circuit Diagram Amplifier is suitable for almost all types of transmissions, because of the possibility of adjusting the drain current of FET's by P1. For linear applications (AM and BLU), drain current must be adjusted to 20 mA. If is used for FM-CW, P1 will be adjusted so that no current will not flow through the drain rest. For this case, the idle current is 200 mA and between 300 mA. Coils are made on cases with a diameter of 9 mm. Care should be taken to wound as tight turns without any space between them. Coils should be made as follows: L1 = 12 turns enamelled 0.6 mm copper, L2 and L4 = 5 turns ...

The sensitivity of receiver it is possible to increase itself considerably, if is interfered, between this and his aerial, a amplifier RF. 40 MHZ-Wide Band RF Amplifier Circuit Diagram : The amplifier of circuit, does not use in resonant circuits and for this is suitable, so much for mid waves, what for the low waves, up to the 40 MHZ. The gain his it is the order 20db and it consumes 7mA, when it is supplied with 12 until 15V dc. His entry and the exit are adapted with coaxial cable, complex resistance 75ohm. Source : users.otenet.gr

This Audio Receiver 433 MHz RF module using circuit diagram is very interesting, it is a module 433mhz RF common of those used in alarm or electronic gate, which was transformed into audio receiver and data simultaneously. The circuit consists of LM386 audio amplifier and the RF module requires a voltage of 4.5 to 5.5 volts and a very small current. Audio Receiver 433 MHz RF module using Circuit Diagram

RF amplifier protection I have developed the protection circuit for the EB104 amplifier I am working on, after I finally had some time to design and test a few models. The main requirements have been: - protection in case of high temperature; - protection in case of high SWR; - protection in case of wrong output filter selection; - simple design (i’m a fan of the whole K.I.S.S. rule of thought), able to work in strong electromagnetic fields, reliable, inexpensive. Because i will be using the same directional coupler i have used in the SWR meter (the one made on PCB) wich is directly influenced by the signal frequency, and because i want full HF coverage, i cannot just measure the reflected signal and make a circuit cut the amplifier when it goes over a limit; on 28Mhz the coupler generates roughly 4 times more voltage that let’s say in 7Mhz. So a system that compares direct and reflected signal and triggers when the latter is percentually too high was needed, therefore an operational a...