This is a small battery operated Tracking transmitter which broadcasts a repeating radio signal which can be detected by a directional antenna. The transmitter broadcasts an isotropic (radiates in all directions) signal on the FM band. An ordinary FM radio can be used to locate the transmitter, the reception of the signal will improve when the rad
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io antenna is pointed in the direction of the transmitter. The transmitter is a standard hartley oscillator, designed to transmit across the FM band approximately, 87 to 108MHz. The transmit frequency is adjustable by means of trimmer C8. The combined capacitance of C4 plus C8 and L1 set the resonant frequency. Modulation for the transmitter is an interrupted square wave signal using all 4 gates of a CD 4011. Gates U1 and U2 interrupt the signal at about 2Hz while gates U3 and U4 create a higher tone in the audio range. The output of U4 applies this modulation to the base of Q1 via R3. Because the modulation is a squarewave, the radiated signal becomes a little bit "dirty" and harmonics will be heard across the FM band. This is not a big problem as it will aid in locating the transmitter. The transmitter is tuned by the tank circuit L1 and parallel capacitance of C4 plus C8. L1 is approximately 0. 15 uH. The value of "C" in the equation below is the sum of C4 plus C8. L1 is 7 turns of 20swg wire wound on a 6 mm drill bit. This forms an inductor of approximately 150 nH. The value of the inductance can be altered by compressing or expanding the turns. Hold one end of the wire against the drill bit and start to wind the turns clockwise. Continue until all 7 turns have been completed, and the coil looks like the image of the right hand side. Trim any excess wire so both ends are same length and scrape about 3mm of insulation...
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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