Fm-snooper

Posted on Sep 29, 2012

The FM Snooper is an FM transmitter that radiates a continuous wave whose frequency is altered according to the sound waves striking the microphone. An ordinary FM broadcast receiver detects the transmitter`s output carrier. When 9-V battery, B1, is connected, a brief surge of current flows from the collector to the emitter of Q1, causing an alternating current, shock oscillation in the resonant LC circuit, to flow back and forth between L1 and C5.

Click here to download the full size of the above Circuit.

So, by varying the value of C5, you can tune the oscillations to the exact frequency desired. Although tuning capacitor C5 accounts for the major part of the tuning capacitance, the capacitance between the base and the collector of Q1 has a small, but noticeable, effect on the oscillation frequency. That capacitance. which is known as the junction capacitance, is not a fixed value, but instead varies when the voltage on the base of the transistor varies. Sound waves striking the microphone induce a voltage that varies in time with the sound. That voltage is applied via C1 to the base of Q1, thereby frequency modulating the transmitter.

Leave Comment

characters left:

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

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....
Ultrasonic distance finder circuit

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....
Simple Metal detector circuit with CD4030

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....
Fully automatic watering circuit for flower pots

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....
Simple deep searching metal detector circuit

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....
Sub-Harmonic Bass Converter for Electric Guitars

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,....
Echo Depth Sounding Sonar for Boats

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....
100W HiFi Audio Amplifier Circuit

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....
Plant-Pot Water Level Indicator Circuit

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.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Simple-high-voltage-supply

This circuit can generate high-voltage pulses with an inexpensive auto ignition coil. Add a...

bjt transistor circuit finding the resistances

I have been given the following circuit diagram and have been asked to compute R2 and RC such...

Zipper Sensor

I used 45 peices of 220 ohm resisters to make 10k ohm variable resister. By banding the wire of...

Sound Synchronized LED Video Tutorial

Is possible to syncronize the leds so that first, the speakers are still playing aloud, and two,...

Nicad Charger Uses Voltage Cut-Out

This circuit charges two NiCad cells with a constant current and features dual charging rates,...

Simple circuit diagram repellent

A very cheap and simple repellents can be used for rats, mice and other animals may use...