PC Audio To FM transmitter

Hi

My name is Adithya from a small city in India.

I am trying since 1+ week to build a FM transmitter which accepts audio out from computer and transmits it in FM range which i will pick up with my mobile FM. So kind of wireless headphone

I have these problems :

1. Limited knowledge about electronics So cant make very complex circuits

2. Lack of many components in city like nano farad capacitors, inductor wires etc. We have pico,micro fard capacitors but not nano and no inductor wires are available here Fixed value inductors are available

3. The FM transmitter should run by 5 V since i am drawing 5V from USB.

4. Instead of microphone in FM transmitter i am using audio out. I am sure the resistor values will change in case of audio out.

I have obtained 74LS73IS,BC547,2N2222A transistor
So any way to make a good range of FM say within 2 room in my house using these. Resistors are not problem i can get any value but no capacitors with nano farad values and inductors coils are available

---------- Post added at 00:38 ---------- Previous post was at 00:34 ----------

I have tried following circuits replacing capacitors of nano farads with more nearer pico/micro farad capacitors and replacing microphone with audio out

Hello Adithya,
I gave a look at the circuit.
Unless I am completely wrong, you will be never able to build a wireles headphone with this circuit. This device seems designed for a different purpose, in facts I think it's a simple noise detector. The sound level at the microphone determines the voltage at pin 5. When its value goes beyond the "logical 1" threshold, the "oscillator" (a loop between input and output of an inverting gate) is released and a signal of constant frequency is transmitted. Conversely, if the value is below "logical 0" threshold, the oscillation stops.
The capacitor gives you some control over the frequency, in a very brutal way. Increasing the capacitor decreases the frequency.

Thanks for the reply kalbun
Yeah the circuit didn't worked
Can you please suggest a circuit which can be used as a FM transmitter for audio out signals of Computer. I searched everywhere but didnt found any such circuit

This circuit is close to what you want: FM Transmitter USB but it has some components that may be difficult for you and it needs a pre-emphasis circuit: **broken link removed**.

KJ6EAD said:

This circuit is close to what you want: FM Transmitter USB but it has some components that may be difficult for you and it needs a pre-emphasis circuit: **broken link removed**.

Click to expand...

Thanks for the reply KJ6EAD.
Many components,IC's in the circuit are not available and the circuit is complex. I am doing the circuit in bread board and will keep it like that only since i dont know how to make PCB and i dont have to required tools to make it

problem with transistor based FM transmtter is that output freq. is not fixed . so if u use digital FM receiver such like in ur mobile phone u will be unable to receive signal. so u have to use manual analog radio receiver to receive ur signal. I think a lots of transmitter ckt available on web . one thing is that BC547 is not useful for FM generation . U have to use VHF range BJT such like BF494 etc.

subir.2006 said:

problem with transistor based FM transmtter is that output freq. is not fixed . so if u use digital FM receiver such like in ur mobile phone u will be unable to receive signal. so u have to use manual analog radio receiver to receive ur signal. I think a lots of transmitter ckt available on web . one thing is that BC547 is not useful for FM generation . U have to use VHF range BJT such like BF494 etc.

Click to expand...

Oh this is new thing to me. So i cant use mobile for receiving generated FM signal and have to rely upon analog reciever ??
There are many many circuits in net but some are complex,some components are not available,some operate on 9v Dc with microphone etc
So no circuit for my need and limitations

adithyau said:

We have pico,micro fard capacitors but not nano

Click to expand...

This may seem like a dumb response, but you say you have limited knowledge about electronics.

Do you know how to convert between nano, pico, and micro? ie. 10nF = 0.01uF = 10,000pF.

It may be that your source for capacitors just expresses the value in a different form.

Off course yes and i have asked the equivalent value in pf but they have told me its not available