This circuit generates a low power test signal and should not be used as a transmitter. Make sure you are within the law in the locality in which you operate this. As this was built from parts laying on the bench, it isn't optimized, but it does demonstrate that it is very tolerant of component choice. A lot of small signal transistor will work. Look up the 2N4401 -its not that special. Be aware that the antenna has DC on it and shorting the antenna to ground might destroy some of the parts. You can use a small (.001 uf for example) capacitor in series with the oscillator output if you want. If you use an antenna with this device, make is a really short one as RF emissions are regulated in most if not all countries. Besides, the waveform is pretty rich in harmonics.
Click here to download the full size of the above Circuit.
A while back I needed an amplitude modulated signal source at 4 MHz. This circuit was literally thrown together with parts laying on the bench. I built it dead bug style on a piece of copper clad board. It should work for you with little or no modification, other than the selection of the crystal, for use at other frequencies. At lower frequencies you might have to increase the capacitor values to get it to oscillate, and at higher frequencies, you might have to reduce the capacitor values a little. Just be aware that the crystal will be operating in its fundamental mode. Overtone crystals will work, but they will oscillator at their fundamental frequency.
Output level can be raised by biasing the audio amplifier's output stage to a higher voltage. This can be accomplished by placing a resistor from the base of the grounded-emitter transistor to ground. As voltage to the oscillator is increased, the voltage swing to achieve a given level of modulation will have to be increased as well.
The gain of the audiio amplifier is determined by the ratio of the 1 K ohm input resistor to the 56 k Ohm feedback resistor, and is limited by the open loop gain of the grounded-emitter stage. The open loop gain can be estimated by looking at the voltage drop across the 1 K ohm collector resistor. The voltage gain will be (in theory) about 38 X the voltage across the 1 K collector load. Thus, a 2 volt drop would give you an open...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: