Here's a rewritten and improved version of the original text in English, with added content to make it more natural and engaging, while keeping the core information intact. The total character count is over 500:
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A compact transmitter introduced here is ideal for beginners who are just starting out in radio electronics. The circuit design is simple and easy to build, making it affordable and accessible. It operates at a low power level, typically between 5 to 8 mW, and can transmit up to 300 meters within a house or small area. It uses a standard FM radio for reception, proving its clarity and sensitivity. One of the most challenging aspects of this project is achieving transmission with just a 3V power supply and a half-wave antenna. Additionally, since the circuit requires very few components, it can easily fit inside a matchbox—slightly larger than a regular matchbox.
This device is not only practical but also discreet, making it suitable as a hidden bug or surveillance tool. However, its applications go beyond that. It can be placed in a baby’s room, near a door, or in a hallway to monitor situations in real-time. It can also serve as a night-time security device, offering a simple yet effective solution for basic monitoring needs.
The circuit consumes less than 5 mA of current, allowing it to run continuously for 80 to 100 hours on two standard dry batteries. It remains stable under normal operation, with minimal frequency drift. During testing, after running for 8 hours, no recalibration of the receiver was needed. The only factor affecting the output frequency is the battery condition. As the battery ages, there may be slight changes in frequency, but this is negligible for most applications.
Building this transmitter is an excellent way to learn about FM transmission. You’ll quickly realize how efficient and high-quality the signal can be, even with low power. The absence of noise makes it especially impressive. The circuit consists of two main stages: an audio amplifier and an RF oscillator. There's actually a FET built into the electret microphone, which can be considered as a third stage if desired. This FET amplifies the capacitance changes from the microphone’s diaphragm, contributing to its high sensitivity.
The audio amplifier stage uses transistor Q1, which provides a gain of approximately 20 to 50. The amplified signal is then sent to the base of the oscillation stage. The oscillator stage, based on transistor Q2, operates around 88 MHz. This frequency is controlled by a 5-turn coil and a 47pF capacitor. The transistor itself, along with a 18pF feedback capacitor, and biasing components like a 470Ω emitter resistor and a 22kΩ base resistor, also plays a key role in setting the operating frequency.
This project is not only educational but also fun to build. It offers a hands-on approach to understanding wireless communication and the basics of FM transmission. Whether you're a hobbyist or a student, this little transmitter is a great way to get started in the world of radio electronics.
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Let me know if you'd like a more technical or more casual version!
Voltage Stabilizer
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TTN voltage stabilizer has the low energy consumption,the over voltage protection,the low voltage protection,the over-current protection,the over-loading protection,the over-temperature protection and so on.It boasts for many kinds of protections,the collection energy conservation and the environmental protection ect.This is a brand-new concept product which possess many new technologies!This series products simultaneously are applied for many technical monopolies
We already applied many kinds of this products patent, and the technical patent NO: 200720036394.1   and Appearance paten NO: 200730025909.3
2. Use for equipment:
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  Copy machine
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  Industrial automation equipment
  Color and drying equipment
  Test equipment
  Hi-Fi equipment
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Voltage Stabilizer,Voltage Stabilizer For Ac,Voltas Stabilizer,Power Stabilizer
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