Electronic Circuits Schematics Projects




RF Circuits


Radio frequency (RF) is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist.

Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies. The energy in an RF current can radiate off a conductor into space as electromagnetic waves (radio waves); this is the basis of radio technology. RF current does not penetrate deeply into electrical conductors but flows along their surfaces; this is known as the skin effect. For this reason, when the human body comes in contact with high power RF currents it can cause superficial but serious burns called RF burns.
 
In order to receive radio signals an antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range).[1] This is typically done via a resonator in its simplest form, a circuit with a capacitor and an inductor forming a tuned circuit. Radio frequency (RF) energy has been used in medical treatments for over 75 years,[3] generally for minimally invasive surgeries, using radiofrequency ablation and coagulation, including the treatment of sleep apnea.[4] Magnetic resonance imaging (MRI) uses radio frequency waves to generate images of the human body.

People are requesting walkie-talkie and RF remote control schematics, so here are some. Building these circuits needs special equipment and expertise in RF circuits. If you have no experience in RF, I suggest that you choose the easy way and buy a ready-made RF module. Otherwise you can realize you have an exact copy of a circuit in your hand, still it doesn't work the way it should. 100s of RF circuits for every hobbyist, technician, student, and design professional. An nice reference tool which includes lots of rf circuits. look at these circuit ideas, some of them may need some modification if they are to work as advertised. Ideas along with pretty good descriptions for each circuit.

 

High Power Portable TV and FM Jammer circuit New

There are still neighbors that keep annoying you by having loud the TV or the radio? Well I have you the solution. In fact all neighborhood will face your jamming waves at their TVs and radios, so be careful. This Jammer is the improved version of the old "TV and FM jammer schematic" with the difference of much higher power. Many of you where asking for a stronger and wider effect but to be as portable as can be. Looking at the schematic you can see that, only the.....


Views: 16 | Votes: 1 | Comments: 0 | Rating: 7 | Rank: 9 | Added: May 21, 2013 |
Beacon-transmitter

This transmitter can be used for transmitter hunts, for remote key finding, or for radio telemetry in model rockets. It can be tuned to the two meter band or other VHF bands by charging Cl and Ll. 11 is four turns of #20 enameled wire airwound, 0.25 inch in diameter (use a drill bit), 0.2 inch long, centertapped. The antenna can be 18 inches of any type of wire. IC2 functions as an audio oscillator that is turned on and off by IC1 about once per second. ..


Views: 45 | Votes: 4 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Apr 1, 2013 |
Vlf converter

This converter uses a low-pass filter instead of the usual tuned circuit so the only tuning required is with the receiver. The dual-gate MOSFET and FET used in the mixer and oscillator aren"t critical. Any crystal having a frequency compatible with the receiver tuning range may be used. For example, with a 3500 kHz crystal, 3500 kHz on the receiver dial corresponds to zero kHz; 3600 to 100 kHz; 3700 to 200 kHz, etc..


Views: 5382 | Votes: 74 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Mar 31, 2013 |
Atv Jr Transmitter 440Mhz Circuit

This low-power video transmitter is useful for R/C applications, surveillance, or amateur radio applications. Seven transistors are used in a crystal oscillator-multiplier RF power amplifier chain, and a high-level video modulator. A 9- to 14-Vdc supply is required. ..


Views: 43 | Votes: 96 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Mar 31, 2013 |
140W amateur radio linear amplifier 2-30Mhz

This inexpensive, easy to construct amplifier uses two MRF454 devices..


Views: 1403 | Votes: 106 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Mar 30, 2013 |
High power mobile phone Jammer circuit

If we are speaking about professional Cell phone Jammers we are talking about this schematic below. First off all you should be very careful how to use this device. Its fully illegal and so the purpose I post this Circuit is only for educational and testing reasons. This type of device is being used by security for VIPS, specially at their limousines to avoid bomb triggering while the car passes from the target cell phone-bomb. Offcourse there are those who use it to make.....


Views: 2398 | Votes: 8 | Comments: 0 | Rating: 8.125 | Rank: 10 | Added: Mar 29, 2013 |
Line driver provides full rail excursions

The logic input is applied to opto-isolators Ul and U2 with, respectively, npn and pnp emitter follower outputs. Dc balance is adjusted by potentiometer R2. The emitter followers drive the gates of Ql and Q2, the complementary TMOS pairs. With a ±12 V supply, the swing at the common source output point is about 12 V peak-to-peak. By adding a ± 18-V boost circuit, as shown, the output swing can approach the rail swing. ..


Views: 344 | Votes: 10 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Mar 25, 2013 |
4-18Mhz-converter

The unit consists of rlamplifier Q1, local oscillatorQ2, and mixer Q3. The two bands are covered without a bandswitch by using an i-f or 3.5 MHz. The oscillator range is 7.5 to 14.5 MHz. Incoming signals from 4 to 11 MHz are mixed with the oscillator to produce the 3.5-MHz i-f. Signals from 11 to 18 MHz are mixed with the oscillator to also produce an i-f of 3.5 MHz. At any one oscillator frequency, the two incoming signals are 7 MHz apart. ..


Views: 32 | Votes: 1 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Mar 19, 2013 |
Transistorized Am Radio Circuit

Shown is a schematic of a typical transistor AM radio. This circuit uses npn transistors. The circuit is generic; therefore, no specific values are given for some components...


Views: 56 | Votes: 5 | Comments: 0 | Rating: 7 | Rank: 5 | Added: Mar 18, 2013 |
Switchable Vhf Active Antenna Circuit

The AA-7 active antenna contains only two active elements: Ql (an MFE201 N-chanriel dual-gate FET) and Q2 (a 2SC2570 ripri VHF silicon transistor), which provide the basis of two independent,..


Views: 50 | Votes: 8 | Comments: 0 | Rating: 3 | Rank: 5 | Added: Mar 17, 2013 |
45Mhz If Amplifier With Crystal Filter Circuit

A 40673 dual-gate MOSFET is matched to a crystal filter at 45 MHz. The filter impedance is around 2kQ...


Views: 25 | Votes: 88 | Comments: 0 | Rating: 5 | Rank: 5 | Added: Mar 17, 2013 |
Vlf/Vhf Wideband Low-Noise Active Antenna Circuit

A 30- to 50-cm whip antenna provides reception from 10 kHz to over 220 MHz. Tl, a dual-gate MOSFET, provides low noise, high-input impedance, and high gain,..


Views: 51 | Votes: 33 | Comments: 0 | Rating: 9 | Rank: 5 | Added: Mar 11, 2013 |
CW signal processor

This circuit provides interferenced rejection for the CW operator. The 567 phase-locked loop is configured to respond to tones from 500 to 1100 Hz. The Schmitt trigger reduces the weighting effect caused by the output of the PLL remaining low after removal of the audio signal. Ten to 15 millivolts of audio activate the circuit..


Views: 813 | Votes: 57 | Comments: 0 | Rating: 2 | Rank: 5 | Added: Mar 2, 2013 |
450Mhz-common-gate-amplifier

This is a low noise, 3-dB typical NF, amplifier with about 10-dB gain at 450-470 MHz ..


Views: 20 | Votes: 5 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Mar 1, 2013 |
1W Linear FM Booster

That RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear with BGY133 or BLY87 and so on. Its power supply has to give 500mA current at 12 Volts. More voltage can boost the distance but the transistors will be burned much earlier than usual.! In any case do not exceed the 15Volts. ..


Views: 3465 | Votes: 1 | Comments: 4 | Rating: 9 | Rank: 10 | Added: Feb 27, 2013 |
Fm demodulator

The NE564 is used as an FM demodulator. The connections for operation at 5 V and 12 V are shown in Figures 21-4A and 21-4B. The input signal is ac coupled with the output signal being extracted at Pin 14. Loop filtering is provided by the capacitors at Pins 4 and 5 with additional filtering being provided by the capacitor at Pin 14. ..


Views: 869 | Votes: 0 | Comments: 0 | Rating: 0 | Rank: 0 | Added: Feb 26, 2013 |
Low-cost-line-receiver

This timer makes an excellent line receiver for control applications involving relatively slow electromechanical devices. ..


Views: 11 | Votes: 22 | Comments: 0 | Rating: 8 | Rank: 5 | Added: Feb 25, 2013 |
Agc System For Ca3028 If Amplifier

An MPF102 amplifier feeds IF signals to a 2N4126. A potentiometer in the MPF102 source acts as a gain co..


Views: 25 | Votes: 76 | Comments: 0 | Rating: 9 | Rank: 5 | Added: Feb 25, 2013 |
Uhf Tv-Line Amplifier

This circuit offers 10- to 15-dB gain from 400 to 850 MHz and is therefore eminently suitable for situations where th..


Views: 27 | Votes: 20 | Comments: 0 | Rating: 4 | Rank: 5 | Added: Feb 24, 2013 |
Wideband Antenna Preamplifier Circuit

This wideband antenna preamplifier has a gain of around 20 dB from 40 to 860 MHz, covering the entire VHF, FM, commercial, and UHF bands...


Views: 48 | Votes: 32 | Comments: 0 | Rating: 3 | Rank: 5 | Added: Feb 24, 2013 |
 
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