Radio circuit diagrams electronics projects for radio transmitter, radio receiver circuit, rf amplifiers, rf boosters and some other related RF circuits like: fm antenna booster, microwave transmitter and wireless modules.
This 20dB antenna amplifier is a very simple antenna amplifier circuit that use few common transistors ant some resistors .
This antenna amplifier circuit can be useful for signal waves with a frequency between 0.1 to 400 MHz and has a gain around 20dB . T1 transistor must be BF200 type (or similar ) and the other transistors can be BF214 type . For high efficiency , the antenna amplifier must be placed at a small distance from antenna .
This amplifier circuit can be powered using a power supply that supply an output voltage between 6 and 12 volts DC . For powering this device you need to use a shielded cable or a coaxial cable .
An very simple and useful active antenna can be constructed using this electronic circuit diagram . This active antenna is based on transistors and other few common components . Because in practice of frequency short-wave reception, the general rule is that if the used antenna is longer , the stronger the received signal will be we need in some cases ( when we can not built a big antenna , because of some factors ) .This RF circuit provide a 14-20dB gain at the popular short-wave and radio-amateur frequencies of 1-30MHz. Antennas that are much shorter than 1/4 wavelength present a very small and highly relative impedance that is dependent on the received frequency. It is difficult to match impedances over a decade of frequency coverage. For this RF circuit a gain of 20dB is typical from 1-18 MHz, decreasing to 14dB at 30MHz.
For this active antenna circuit many different types of JFET's may be used , such as the MPF102, NTE451, ECG451 or 2N4416 and 2N3904 or 2N2222 transistor works well for Q2, Q3, and Q4 .
The most important thing of Q3 transistor circuit parameter is the voltage drop across R8: the greater the drop, the greater the gain.
Transistor Q4 transform Q3's relatively moderate output impedance into a low impedance, thereby providing sufficient drive for a receiver's 50-ohm antenna-input impedance.
This RF circuit needs to be powered by a 9 volts battery or a 9 volts DC external adapter .
This electronic rf detector circuit diagram is based on common transistors and other few common components . This rf detector responds to RF signals bellow the standard broadcast band to well over 500 MHz and provides an visual , and audible indication when the signal is received . By adjusting the bias of D2 with the R2 potentiometer the circuit can detect low power or strong signals . A very sensitive setting can be obtained by modifying the R2 until the LED begins to light .
As you can see in this rf detector circuit diagram , the indications is given by a piezo buzzer an a LED .
The circuit can be powered using a simple 9 volts battery or any other 9 volts DC power supply circuit . If the rf detector is not enough sensitive you can connect a good wideband RF amp between the antenna and the detector diode .
Keep diode and capacitor (C1) leads short to minimize stray inductance. The used transistors can be : 2N3906 ,2N2907 or other PNP high gain transistor for Q2 and PN2222A , 2N3904 or other NPN high gain transistor for Q1 .