fm transmitter using colpit oscilator

[abdullah8391]

Hi everyone, i have chosen to make an fm transmitter as my semester project. but after several days of research, I couldn't get many answers.
I know:
1. signal received would be maximum of 150 mV, and I need to amplify its current and voltage.
but how?(i.e through common emitter or common collector?).

2. I need to generate 90 MHz frequency, and modulate the input sound signal with generated 90 MHz signal.
but how will it modulate and how should I design it? because the attached pic doesn't satisfies theoretically.

So i shall be really great full if you could provide me with links how to design it. Or at least tell my if you know anything about it.

I shall be really grateful for quick response because I have to submit it's working simulation by Monday.

 

[Arouse1973]

Is your current circuit not working? Where did you get the circuit from?
Adam

 

[abdullah8391]

Is your current circuit not working? Where did you get the circuit from?
Adam

we are tying to make our own, above attached picture is my own design with some hit and trials.
since it is the second half of the circuit, so I can't understand how to design first half.

Basically I don't know how much voltage and current of each part of circuit should have and i couldn't find it on net either.
So it will be a huge help if you tell me how much voltage and current i should amplify in first part, and amplitude of signals generated from colpit.

If you know any guaranteed FM transmitter working then please tell me about that. I could back track that circuit and many of my questions will be cleared.
and regarding the circuits available on net, on what basis do the use copper wire?
e.g in the circuit of given link:
http://kpkpkalpesh.blogspot.com/2011/12/fm-radio-transmitter.html

 

[Arouse1973]

Here is a circuit that will oscillate. You will have to adjust the component values for your own. I just added some values I thought might work.

 

[abdullah8391]

Thanks arouse, but as i mentioned earlier, i already have designed colpit(it's an oscilator).
That was the 2nd half part of the circuit.
For 1st part, I need to ampify the signal. So how much should i amplify and through which transister biasing(we are bound to use transistor amplifier). I can't use common emitter because it causes phase inversion, so which else should i use?

 

[Alec_t]

I can't use common emitter because it causes phase inversion

Why does phase inversion matter? The phase of any audio signal is continuously changing; an extra 180 degrees is of no consequence.

 

[Arouse1973]

Yes correct Alec, you beat me to it. I dont think the OP knows what he wants.
Adam

 

[Arouse1973]

Thanks arouse, but as i mentioned earlier, i already have designed colpit(it's an oscilator).
That was the 2nd half part of the circuit.
For 1st part, I need to ampify the signal. So how much should i amplify and through which transister biasing(we are bound to use transistor amplifier). I can't use common emitter because it causes phase inversion, so which else should i use?

Just put a simple audio amplifier at the front end and couple in with a capacitor.

http://www.google.co.uk/search?q=co...hUBkRQKHduqB2QQ_AUIBSgB#imgrc=N4f-P0BsXN3UCM:

 

[Alec_t]

That works for AM, but the OP specifies FM?

 

[Colin Mitchell]

The component values are all incorrect in your circuit for 90MHz.

 

[BobK]

I doubt that either of those circuits will get to 90MHz.

Bob

 

[abdullah8391]

Friends can you suggest one?

 

[Colin Mitchell]

Learn from here: Spy Circuits

 

[abdullah8391]

Learn from here: Spy Circuits

thanks a lot bro.
This link really helps!!!!!!!

 

[Arouse1973]

That works for AM, but the OP specifies FM?

Sorry Alec what do you mean, are you saying the circuit is not an FM circuit? Or was your reply not for me?
Adam