27mhz intercom walkie talkie circuit

Posted on Feb 6, 2014

Intercom walkie talkie are the next logical step in this discussion. They show how a crystal oscillator can be used to transmit voice. Transmitting a voice via a crystal locked oscillator is not easy. This is because the crystal is locking the frequency and it is very difficult to shift it. The only way to do it is to add the audio as an amplitude

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

component so that the amplitude of the oscillator rises and falls with the audio signal but its frequency does not change. This is the figure of the circuit; Nearly all the components in the 4-transistor circuit are used for both transmitting and receiving. This makes it a very economical design. The frequency-generating stage only needs the crystal to be removed and it becomes a receiver. The operation of this circuit coincides with our discussion on receiver circuits at the beginning of this article where we said the receiver was oscillating all the time, similar to a weak transmitter. A 390R is added to the emitter of the oscillator stage to reduce the activity and turn it into a receiver. The next section of the circuit is called a building block. It consists of three transistors directly coupled to produce an audio amplifier with very high gain. The first transistor is a pre-amplifier and the next two are wired as a super-alpha pair, commonly called a Darlington pair to drive the speaker transformer. The third block is the speaker. This is a separate item because it is used as a speaker in the receive mode and a dynamic microphone in the transmit mode. A speaker can be used in reverse like this and it is called a dynamic microphone because of the coil and magnet arrangement. When you talk into the cone, the movement of the voice coil in the magnetic field produces a few millivolts output. This can be coupled to a high...

Visit page

Leave Comment

characters left:

Related Circuits

Make this Fancy LED Tail Ring Light Circuit for your Car

The following article describes a fancy LED sequencing/diverging ring type light which can be used as a tail brake light in cars. The circuit idea was requested by one of the avid readers of this...

RS232 Reset for Microprocessor

This circuit allows a remote microprocessor to reset the control of a host by sending an interrupt signal on an RS-232 or RS-422 serial line. If the remote machine is restarted on a simple program...

Infrared Cordless Headphone Amplifier

Using this low amount Project one can carbon AUDIO from TV after advancing anyone. It does not use any wire amid TV and HEADPHONE. In abode of brace of affairs it uses airy Infrared ablaze to...

XR2212 PLL FM demodulator Circuit

A simple PLL FM demodulator circuit using IC XR2212 is shown here. XR2212 is a highly stable, monolithic PLL (phase locked loop) IC specifically designed for communication and control system...

Circuits Diagram: Simple 40W inverter

This is the schematic of a simple 40W, 12 to 220 V inverter. You don`t believe, this is simple and cheap and working for me for last 4 years. The heart of the circuit is a CD 4047 IC which is wired...

SimpleCircuit IF Signal Generator

Here is a able ambit of IF arresting architect which may be of absorption to radio hobbyists and professionals alike. Transistors T1 and T2 anatomy an astable multivibrator aquiver in the audio...

Simple variable frequency oscillator circuit

Single Differential Input Adapter for Digital Voltmeter

I some cases, a cogwheel ascribe is bare for voltage measurement. Using the alone one operational amplifier, you can body an adapter to accommodate a amphibian ascribe for your ground-referenced...

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

rs232 to rs485 circuit

The new archetypal of RS485 advocate overcomes the RTS controlled botheration accomplished by our...

Credit card sized ethernet arduino controller

I love the Arduino as a simple and accessible controller platform for many varied projects. A few...

555 timer compo entry 2

This entry is a 4 step sequencer controlling an `Atari Punk` synth with a greyscale NTSC video...

Fog Lamp Sensor Circuit

A rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under...

Simple Active Mixer on sinlge voltage

It`ll work on single supply. I`ve used it when I ran my lunetta on a 9 volt battery for a while...

Dual timing circuit thyristor control table

Electronic Table (1) Introduction This schematic circuit having two alarm output by the timer by...