5KM Transmitter Circuit Diagram

 5km radio transmitter circuit

Simple Shortwave(SW) transmitter circuit diagram using BD 139 transistor.

The power of this transmitter is around 2 watts.The frequency is 3.579 MHz.We can use any crystal under 10 MHz.But using a 3.579 MHz is preferred.As this is a shortwave transmitter a less power will reach greater distance using long anntenna or half wave dipole antenna.In Some cases range can be of 100 of kilometer.

Working

In this project we took a BD139 transistor which is best suited for shortwave transmission for beginners.As this transistor is cheap and readily available in any electronic stores.

  

As you can see in the diagram the transistor's base is biased to the positive 12 volts supply.Hence it's an NPN transistor we are doing this type of biasing.The transistors base terminal is connected to a crystal(3.579 MHz).This generates a carrier frequency in the AM frequency band.The inductor value is around 100 microhenry which powers the transmitter to radiate rf signal to the output world.Using an antenna the signal is propagated.

  The base terminal of the transistor is coupled to 1mfd/63 volt capacitor.This is to remove DC values entering to the base terminal of the transistor and only AC signals can enter into the transmitter base.

The audio is fed in the capacitor using a 10 kiloohms resistor.Its not necessary that we must use this value of resistor.We can use any resistance value here depending upon the audio signal current.By using a stereo/mono pin audio can be fed to the transmitter.

 

Advantages

* Easy to buld

* Component availability is cheap and easy to find

* Travel greater distances along the earth surface and they are usually called as sky waves.

Troubleshooting Transmitter

In some cases even if you build such small transmitters, it's not going to work properly.In such cases remove the audio signal fed into the transmitter.Change the 10k value to a larger values and test the transmitter again.

  

The audio received is not audiable in some Cases.Firstly test the stereo pin with a headphone and  check an audio test.

   Audio volume is low circuityep.com - Increase the volume of the audio feeding device or remove the base resistor and replace it with a low value resistor.

Components Used : 

* Transistor - BD 139 

* Resistor     - 10 kilo ohms of 2 nos 

* Capacitor  - 10 mfd/63v

* Inductor    - 100 micro henry 

* Crystal       - 3.579 MHz 

5KM Transmitter Circuit Diagram

Circuit Diagram :

5km transmitter circuit diagram

For Amazing & Simple Electronic Projects 

For Automatic Plant Watering System Project Click Here