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FM Beacon Transmitter circuit – Circuit Schematic
FM Beacon Transmitter circuit
This circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws...
AM Broadcast Transmitter schematic – Circuit Schematic
AM Broadcast Transmitter schematic
In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configurati...
Crystal Radio III – Circuit Schematic
Crystal Radio III
This is basically a crystal radio with an audio amplifier which is fairly sensitive and receives several strong stations in the Los Angeles area with a minimal ...
Loop-stick Antenna for AM band – Circuit Schematic
Loop-stick Antenna for AM band
Wound on a 3 foot length of PVC pipe, the long loopstick antenna was an experiment to try to improve AM radio reception without using a long wire or ground. It ...
Pocket Radio AM / FM circuit – Circuit Schematic
Pocket Radio AM / FM circuit
Earphones, batteries are sold separately. AM / FM seems to be a common mold. But stamping is different. AM / FM E193577 UL94V0 board with the AM / FM etching pr...
Wide band 10MHz 500MHz RF amplifier – Circuit Schematic
Wide band 10MHz 500MHz RF amplifier
This paper describes an RF amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz. These kind of amplifiers are called wide band amp...
Dipole antenna for two metres – Circuit Schematic
Dipole antenna for two metres
Described here is a simple omnidirectional, vertically-polarised dipole for two metres. Made from coaxial cable, it can be rolled up and stored in a small conta...
Regenerative receiver for AM band – Circuit Schematic
Regenerative receiver for AM band
The regenerative detector uses a field effect transistor (FET). Like with the better valve designs, feedback is controlled by a variable capacitor. A ferrite ro...
RF meter probe – Circuit Schematic
RF meter probe
This probe is useful for any low level RF work, and simply connects to your multimeter. The voltage shown will not be accurate, since this is a rectifier probe...
Coilless FM transmitter circuit – Circuit Schematic
Coilless FM transmitter circuit
The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in paral...
Colpitts oscillator FM transmitter – Circuit Schematic
Colpitts oscillator FM transmitter
Its frequency depends on the capacitance of the vary cap diode. The center frequency is changed by varying the biasing voltage of the vary cap through the 47K ...
AM power transmitter – Circuit Schematic
AM power transmitter
The circuit for a powerful AM transmitter using ceramic resonator/filter of 3.587 MHz is presented here. Resonators/filters of other frequencies such as 5.5 MHz...
40 meter band Receiver II – Circuit Schematic
40 meter band Receiver II
Using the circuit of 40-metre band direct-conversion receiver descr- ibed here, one can listen to amateur radio QSO signals in CW as well as in SSB mode in the...
Reliable FM transmitter – Circuit Schematic
Reliable FM transmitter
The power output of most of these circuits are very low because no power amplifier stages were incorporated. The transmitter circuit described here has an ext...
0.1Hz to 10Hz RF reciever – Circuit Schematic
0.1Hz to 10Hz RF reciever
The frequency covered is from 0.1Hz to 10Hz and useful signals are received up to 16Hz. The first Op-Amp, properly shielded, must be installed close to the ante...
FM bug circuit – Circuit Schematic
FM bug circuit
This is just one of the many bugging devices available on the eaves-dropping market. The range includes pen and pencil holders, trophies, framed pictures and of...
FM Bug detector 80 - 150 MHz – Circuit Schematic
FM Bug detector 80 - 150 MHz
This Mini FM Bug Detector is basically a broad-band receiver. It picks up the complete band from below 80Mhz to 150MHz and almost anything that transmits in tha...
HF SSB CW AM RF Linear amplifier – Circuit Schematic
HF SSB CW AM RF Linear amplifier
This is a rather unusual QRP Power Amplifier design, with a wide frequency response; within three dB's from 300KHz to 30MHz. Overall gain is in the region of 16...
VHF FM transmitter – Circuit Schematic
VHF FM transmitter
I have had requests to add a VHF FM transmitter, to the QRP collection. This project is a simple transmitter using only one crystal and will cover 145.00 to 146...
High power bug – Circuit Schematic
High power bug
My FM Wireless Microphone has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of...