The circuit below is a standard oscillator of the Colpitts variety. Similar circuits have been used in many ham radio homebrew transmitters. This particular circuit should function well at frequencies from 1500 kHz to 8000 kHz. For use on lower frequencies, the values of C1 and C2 might need to be increased. If you`ve never built a circuit from a
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schematic before, this might be a good one to start with. The diagram below shows how you can arrange the parts on a prototyping board such as Radio Shack catalog number 276-175. (A prototyping board, also called a solderless breadboard, contains groups of holes that are electrically connected. Each hole has a little spring/clamp thingy in it that grabs ahold of the component leads. This is a great way to experiment with circuit designs and learn about the building process. ) Attach a 10-inch (25 cm) piece of bare wire to the output, then sit a radio next to the circuit and tune to the crystal frequency. Apply power. If everything is connected correctly and all the components are in working order, you will hear the carrier (or the silence caused by it) on your receiver. Now all you need to do is add a buffer amp, a modulation stage, a final RF amp, a harmonic suppression and output matching section, and you`ve got an AM transmitter. :-) Below is another version of the circuit with a couple of enhancements. The variable capacitor between the crystal and ground allows you to adjust the frequency slightly. (More capacitance equals lower frequency. ) Q2 serves as a buffer amplifier which stabilizes the circuit and boosts the output power. This circuit was developed independently by another MWA member and uses very different values for R1, C1 and C2 compared to the first circuit on this page; don`t let those differences scare...
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.....
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