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Sunday, June 26, 2011

Build very low cost FM transmitter, use your TV antenna and transmit upto 4km range!!

 Here is the specification of the transmitter


1. No. of stage: 4
2. Frequency of operation: About 100MHz
3. Antenna type: Folded 300 ohms dipole.
4. Range obtained in free space: Up to 4km with dipole antenna 30 feet above ground level. More   range with yagi antenna.

Fig: Circuit diagram of the Transmitter


Brief Description:
The transmitter is built on a Printed Circuit Board. This board uses track inductor for L1, L2 and part of L3. The section built around Q1 is the oscillator section. Oscillation frequency is determined by L1, C4 & C5 which forms the tank. Actually C5 is the feedback capacitor. This is required to sustain oscillation. This also influence the operation of tank formed by L1 & C4. Modulation is directly applied to the base of Q1 via C2. A microphone is connected here to serve this purpose. You can alternately feed direct audio here after disconnecting the microphone biasing resistor R1. Q2, Q3 & Q4 gradually raises the output power up to the desired level.
As most of the inductors are PCB etched, there is practically very little frequency drift provided you use a highly regulated and ripple free power supply.
RF output from the transmitter is taken from the junction of C11 & C12. This is unbalanced output of around 75 ohms impedance. But a folded dipole is a balanced type antenna of around 300 ohms impedance. So we need to use a 'BALanced to UNbalanced transformer' or 'BALUN'. A 1:4 type BALUN is employed here for this purpose. Antenna connection is taken from this BALUN via a 300 ohms flat parallel feeder cable commonly used in television to receive terrestrial broadcast. No coaxia is used to feed antenna. This saves cost. Also a parallel feeder cable provides much less signal loss compared to a coaxial.

 Click 'Read More" to see details with pictures

Success story, making of my FM Transmitter.

I've tried to build (make) my own Fm transmitter from the very beginning of my boyhood but failed failed and failed. My first successful Fm transmitter was aired in 2001 when i was a student of class 12. After a long run of  4 years from class 9.

here i'll show you my recent 10 watt Fm transmitter testing circuit (battery powered exciter only due to security matter) and finally assembled cabinet (AC powered). 



 Transmitter after assambled

 Click "Read More" to see the other photos........

Friday, June 17, 2011

ANTENNA DESIGN FOR FM TRANSMITTE

 ANTENNA DESIGN

There are two types of antenna for FM TRANSMITTE
1. Ground pole Antenna    
2. Half-Wave Dipole Antenna
A ready made GP Antenna. 


1. Ground pole Antenna(GP)

This Antenna is most widely used all over the world. For example, when you

Thursday, June 16, 2011

1 Watt simple FM Transmitter with 1-2 km range!

1 Watt FM Transmitter


This is simple 1 Watt FM Transmitter circuit. This circuit will be able to cover 1-2 KM range with a single pole antenna of 20 feet! 


Click on picture  to view the large size

Descriptions:
P1 act as condenser microphone volume level. For FM, coil will be small. Use thin

Construction of Air Core Coil for FM transmitters

Just follow the steps as shown in the following pictures to make the air core coil for your Fm transmitter






                           Click  "Read More" to view details


USB FM Transmitter Circuit for PC and Laptop

Here's a small FM transmitter ciruit for your desktop or laptop to enjoy the movie and music from a distance. This FM transmitter, which is powered by USB, recovers output on your computer or your MP3 player to the relay on the tape FM (frequency 108 MHz). For Assemblying this FM transmitter kit, an electronics hobbyist will have built in about 30 minutes.



Simpliest 2 watt FM transmitter with PCB and details


 USE DIPOLE ANTENNA FOR MAXIMUM RANGE (COULD BE UP TO 10 KM IN GOOD WEATHER). TUNE BETWEEN 88-108 MHz WITH C5. BB-204 COULD BE REPLACED WITH CONVENTIONAL LED (BIG) WITH REVERSE BIAS (NO LIGHT GIVEN IN CORRECT POLARITY). 9V POWER FOR 2KM WITH GOOD SOUND QUALITY AND GRADUALLY UP TO 18V FOR 10 KM RANGE WITH POOR QUALITY OF SOUND.  BEST OF LUCK. 

Saturday, April 16, 2011

Coilless FM transmitter !

 If you are in the problem to make perfect coils for FM Transmitter then this is your time to go on..... See this coil less and easy FM Transmitter.



The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.

1 km. FM Transmitter

Description

This one is a high power long range (use yagi antenna)  FM Transmitter  that provides very good frequency stability in about 1km range and very good microphone sensitivity. It can be used inside guitars, as a part of remote control systems or in other similar applications.

The features said above are achieved by including an RF amplifier stage with 10dB gain and AF preamplifier stage to boost the modulation.


Thursday, December 30, 2010

Site will be presented with minimum 20 fm transmitter and bug circuits of different range and power. Coming soon. . .

Fm transmitter of 20 km range to 100 meter range will be available here very soon.