HecaWorld One-Transistor FM Transmitter.3GP

One-Transistor FM Transmitter.

Here we used a general purpose NPN transistor to build this simple FM Transmitter.

Any general purpose NPN transistor with ft in the range of radio band of interest will work - ft for this transistor is a minimum of 250MHz. You can find the ft of your particular transistor in the datasheet of the transistor.

All other parts are from old electronics junks. I have built this circuit since my days in the high school and I have used different transistors - C1212, C828, C829, BC108 etc they all worked fine.

My target is to use minimum voltage supply and we did by using this single 1.5V AAA battery. The range is not bad at between 50 and 100 meters with good antenna.

Category:

Science & Technology

Tags:

• Simple FM transmitter
• radio
• Transmitter
• Heca
• Hecanet
• HecaWorld
• James Ugwuogo
• Technology
• HecaTech
• 9J

[7419635841635]

What's the value of the capacitor attached to the antenna?

[hecanet]

@7419635841635 Hey there, use 104 (100nF)...I experimented with various values as well. (10 * 10^4 * 10^-12 = 10 * 10^-8 = 100nF)

[hecanet]

@90asadali Hello Friend...am glad you got it working. That is the first and most important step. Now, you have to play around with your amplifier. Try your amplifier on other signals to make sure the amplifer is working great. If that is confirmed, then try a different pre-amp. I have not had time to work on new pre-amps but I can definitely take a look and recommend some designs later.

[90asadali]

@hecanet one more thing.i am anxiously waiting for your video on walkie talkie using this circuit.when will you upload it??

[90asadali]

@hecanet hey friend i have built the receiver but voice is very low what should i do. i have used amplification stage only. what should i do if my amplification stage does not make a good combo with the pre amp stage shown in your video?

[hecanet]

@90asadali Build ur amplifier & test it separately first. Make sure it works. Use a simple microphone as the input. Then connect the pre-amplifier to it & make sure it works

After those 2, then you are ready to try the FM rcvr

LM741 might not work well. So, try LM 324, 380, 386 or any other amplifier (from 0.5 watts and above)

The idea is to make sure that each stage works on its own before cascading other stages. U might have to tweak the coil & gang to get reception

Grace & Peace!

[90asadali]

@hecanet hi friend..i have made the fm transmitter with the help of your video and now i am trying to build FM receiver but it is not working for me.i put the pre amplification stage after the receiver as shown by you and then took output from speaker but it is not working..should i use another amplification stage after pre amplification?

and for amplification what should i use?? LM 741 or LM 324 or something else??

kindly explain. thanx alot

[hecanet]

@90asadali Hello Friend...to increase the range, you need a higher power supply & add an output RF amplifier.

Use 9 to 12 Volts power supply. Look at the pre-amp in one of our videos & adopt it for the output RF amp. You will need some tuning if you want it to be near perfect.

To avoid repeating efforts, use 1.5 to 3Volts zener diode as a voltage regulator for the transmitter portion. This ensures the frequency does not shift as long as the voltage supply remains above this value.

[hecanet]

@90asadali Hello Friend...Yes, it works on bread board. Try to keep your wires short to minimize stray capacitances.

[hecanet]

@90asadali Hey Friend...any mic works. I used a crystal here. But I have used condenser & dynamic microphones before (a small speaker works as well). I have also used carbon microphone (in my second year at the secondary school I made a simple carbon microphone and it worked for me). You might have to tweak the biasing of the input circuit, though. I can make a video of the carbon microphone (from carbon rod of dead alkaline batteries) if time permits so you can see how easy it is.