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This is the Simple 140W amateur radio linear amplifier 2-30Mhz Circuit Diagram. This inexpensive, easy to construct amplifier uses two MRF454 devices. Specified at 80 W power output with 5 W of input drive, 30 MHz, ana 12 Vdc. Simple 140W amateur radio linear amplifier 2-30Mhz Circuit Diagram

SW Converter for Digital AM Car Radio Circuit Diagram This circuit is purposely presented with many loose ends (not literally, of course) to stimulate experimenting with RF circuitry at a small outlay. Looking at the circuit diagram you may recognize a modified version of the SW Converter for AM Radios described elsewhere in this issue. The modifications were necessary to make the circuit compatible with a digital rather than analogue AM car radio. The main difference between digital AM radios and their all-analogue predecessors is that tuning is in 9 kHz (some-times 4.5 kHz steps) in compliance with the international frequency allocation for the band. Obviously, that particular step size, desirable as it may be on MW, is a stumbling block if you want to use a digital AM receiver in combination with a frequency step-up converter for SW, where chaos reigns and there is no fixed step size. The first attempt was to make the crystal oscillator variable by about 5 kHz each way.   SW Co...

Apart from chucking it in the bin, what can you do with old AM car radio or clock radio in your junkbox? How about turning it into a crystal controlled, stable, short wave radio receiver, for a minimum investment in time and money? Read on. The heart of the circuit shown here is an IC which goes by the name NE602, NE612 or SA612. It is a double balanced mixer that includes an oscillator that can be crystal-controlled, free running or even driven externally from a PLL, etc. It was originally designed for mobile telephones and is probably available in junked car phones from the tip. The NE602/612 contains a differential input amplifier (called a Gilbert Cell), an oscillator/buffer, a temperature compensated bias network and a power regulator. Typical frequency response is in excess of 500 MHz for the input and 100 MHz for the oscillator. Circuit diagram : SW Converter for AM Radio Circuit Diagram   Supply current is 2.4 mA and the absolute maximum supply voltage is 9 V. Input and outpu...

This simple circuit is sure to have the police beating a path to your door- however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat. Simple Radio Wave Alarm Circuit Diagram : Notes : The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or a foot approaches the sensor, the frequency of the transmitter (IC1a) drops appreciably. Suppose now that the circuit transmits at 1MHz. Suppose also that your radio is tuned to a frequency just below this. The 1MHz transmission will therefore not be heard by the radio. But bring a hand or a foot near to the sensor, and the transmitter's frequency will drop, and a beep will be heard from the radio. Attach the antenna to a multiplug adapter that is plugged into the mains, a...

Circuit diagram: Dual Pre-Amplifier for Car Radio Datasheet for AN7310: Download

AM Transmitter circuit  To this powerful AM transmitters are huge, using ceramic tuning 3.587 mhz resonator and resonator filters are also sold with a value of 5.5 mhz, 7.7 mhz and 10.7 mhz. Distance transmitter range is approximately 2-4 km. the working principle of this circuit are filter resonator/ceramic filters raise the frequency of the value of the resonator filter. This frequency is amplified by the transistor can be changed t1. Frequency so need C7 as a regulator / placement. sound signal superimposed over the audio transformer.frekuensi which awakened by resonator filters and t1 is fed to the next amplify strengthened so as to achieve the desired power passed to antenna. t2 and t3 as a buffer as a final power amp. AM Transmitter Schematics AM radio / receiver circuit For AM radio because it's hard to find IC ZN 414 then now could be replaced with the equivalent of IC MK 484. Frequency coverage between 550 kHz-1600 mhz...

Playing cars that are controlled via radio signals is an interesting game. The much-loved toy cars children, plus a simple circuit will be the ideal toy car. This circuit families use traditional digital CMOS IC which requires very little electrical current, so it will not burden the original toy car performance. In this system, radio signals are not transmitted continuously but only generated when the controller sends a command to the left / right or forward / backward, and even then only a radio-frequency discontinuous, so is sending pulses of radio wave frequency. The number of pulses sent represent commands sent, GO command is represented with 8 pulses, is represented with 16 pulses LEFT, RIGHT DOWN 32 pulses and 64 pulses. Commands that can dikirimk is a combination of 2 orders once gus, which is a combination of command forward / backward and right / left, for example, could be sent forward orders and left once gus, in this case the number of pulses sent is 24, ie the sum of the ...

Consider a situation where a burglar has entered your house and snapped the telephone wires, leaving you with no means of communication with the outside world. In such an emergency, you will find this intruder alarm to be very handy. It transmits a prerecorded emergency message repeatedly for reception by an FM receiver. The message containing address, geographical location, name, etc is recorded onto a chip. The prerecorded message can then be transmitted repeatedly with the help of an FM transmitter, in the hope that some noble soul will hear it and inform the police about the incident.   Fig. 1: Block diagram of the intruder radio alert system The circuit comprises a sound recording-and-playback chip (UM5506BH). This chip consists of a 96kbit SRAM and can record up to six seconds of audio. (For details, refer ‘Mini Voice Processor’ circuit published in April 2000 issue of EFY.) After the required message has been recorded, it is passed to a low-power, VHF FM transmitter wired ar...

Playing cars that are controlled via radio signals is an interesting game. The much-loved toy cars children, plus a simple circuit will be the ideal toy car. This circuit families use traditional digital CMOS IC which requires very little electrical current, so it will not burden the original toy car performance. In this system, radio signals are not transmitted continuously but only generated when the controller sends a command to the left / right or forward / backward, and even then only a radio-frequency discontinuous, so is sending pulses of radio wave frequency. The number of pulses sent represent commands sent, GO command is represented with 8 pulses, is represented with 16 pulses LEFT, RIGHT DOWN 32 pulses and 64 pulses. Commands that can dikirimk is a combination of 2 orders once gus, which is a combination of command forward / backward and right / left, for example, could be sent forward orders and left once gus, in this case the number of pulses sent is 24, ie the sum of the ...

This is a simple project of Tuned Radio Frequency (TRF) Receiver Circuit diagram. Super heterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver technologies such as the TRF receiver and the regenerative receiver were still widespread. Tuned Radio Frequency (TRF) Receiver Circuit diagram :   Tuned Radio Frequency (TRF) Receiver Circuit Diagram The circuit described here is based on the old technology, but brought up-to-date a The most important part of the circuit is the input stage, where positive feedback is used to achieve good sensitivity and selectivity. The first stage is adjusted so that it is not quite at the point of oscillation. This increases the gain and the selectivity, giving a narrow bandwidth. To achieve this, the potentiometer connected to the drain of the FET must be adjusted very carefully: optimal performance of the receiver depends on ...

This is a project of Simple Radio Band Position Display Circuit Diagram. This circuit is an add-on unit for radio receivers that lack band-position display. The circuit presented here can show up to nine bands. It also incorporates a novel feature to make the display dance (blink) with the audio level from the receiver. The power-supply for the circuit can also be derived from the radio-set. The conversion of selected channel to BCD format is achieved using diodes D1 through D15 in con-junction with resistors R4 to R7. The voltages developed across these resistors (R4 through R7) serve as logic in-puts to BCD inputs of BCD to 7-segment de-coder IC1 (CD4511). Radio Band Position Display Circuit diagram : Radio Band Position Display Circuit Diagram When all switches are in  ‘off’ state, the volt-age across resistors R4 through R7 is logic zero, but when any of the switches S1 through S9 is slided to  ‘on’ position, the output across these resistors changes to output proper BCD c...