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Radio circuit diagrams electronics projects

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.

AM regenerative receiver

This AM receiver classic design, revamped to use a transistor instead of a vacuum tube applies the principles of regenerative receivers which essentially means that the transistor stage has high levels of positive feedback at a certain frequency the frequency of desired tuning. The stage is operated right below the point of oscillation.
In addition to amplifying the signal, the stage also provides the "detector" function.
This am regenerative receiver circuit project use four 1.5 volt battery cells in series as a power source, or, you can use a 6 volt DC battery or even a 9 volt battery .
This am regenerative receiver circuit works over 1000-mile range (around 1600 km) with a four-foot antenna.

L1 coil must have a 36 turns of #22 on a 4-inch form and C6 capacitor must have a value of 365pf (or L1=72 turns; C6=125pf ).
To adjust this am receiver you must tune R1 until oscillation occurs; back off until is ceases. Now tune C6 for a station, retuning R1 as necessary.
This receiver circuit use a LM386 power amplifier IC that drives a small o ohms speaker . If you connect a mother jack connector like in the circuit diagram , you can use a headset speakers .
Adjusting the 50k potentiometer you can control volume .

regenerative am receiver electronic circuit

Varactorless high frequency modulator

This electronic project circuit is a very simple varactorless high frequency modulator . Traditionally, high-frequency oscillators are frequency-modulated by using a varactor. However, varactors usually require a large voltage change to achieve a reasonable capacitance change ; a problem in many battery-powered systems.

Such a problem can be overcome by employing base-charging capacitance modulation. Resistor R1 establishes Ql's current, and R2 allows control of the collector bias current by Vmod. The transmission line (T1) in the negative resistance type oscillator determines the frequency of oscillation. T1 is a high-quality, low-loss, ceramic coaxial shorted quarter-wave transmission line. Under proper terminal impedances, a negative resistance is "seen" at Ql's base. T1 reacts with this negative resistance to produce sustained oscillations,
Frequency modulation is accomplished by changing Q1's collector bias current and thus changing Ql's base-charging capacitance. This effect is "seen" at Ql's base and causes a frequency shift in the resonators quarter-wave node.
This varactorless high frequency modulator electronic project, must be powered from a simple DC 3 volt power source ( you can use a 3 volt battery) .

varactorless high frequency modulator electronic circuit

50MHz-300MHz colpitts oscillator

In all radio and television applications, the voltage controlled oscillator (VCO) is a varactor tuned, LC type of circuit.
In this electronic project circuit you can see a very simple high efficiency Colpitts oscillator .
In the higher frequency ranges, above 50 MHz, Colpitts oscillators are used because stray circuit capacitance will be in parallel with desired feedback capacitance and not cause undesirable spurious resonances that might occur with the tapped coil Hartley design. The FM VCO shown is a grounded base design with feedback from collector to emitter.

A Colpitts oscillator is one of a number of designs for electronic oscillator circuits using the combination of an inductance with a capacitor for frequency determination. The distinguishing feature of the Colpitts oscillator circuit is that the feedback signal is taken from a voltage divider made by two capacitors in series. As you can see in the circuit diagram , this electronic project require few electronic parts an provide a 50 MHz-300MHz VCO with a tuning range of 2:1 .
50MHz-300MHz colpitts oscillator electronic project


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