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FM transmitter and Reciever

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Korawy

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Hi all,

Im looking forward to building an FM transmitter and reciever.

I have built FM transmitter with LPF and it works well with a good range, and now im trying to build FM Reciever, But I have little knowledge of communication protocols and In fact I will develop the project to send digital data to control machines over FM Band.

The circuits used works well for transmitting and receiving ANALOG Data over FM range, Later I will replace the ANALOG with DIGITAL data (FSK Modulator), So If I use the same Circuit (attached)but instead of ANALOG (audio input) I will use FSK Modulator output, Will it work well ?!

Thanks,

 

Hi. FM is not a band, it is a modulation type; FSK could better be AFSK. FSK implies a fixed modulation tone shifted to a different tone when a key (or data highs and lows) shift the tone frequency, or when the carrier itself is shifted and received in single side band creating a different tone. If your intended modulator can do two tones, may work.
 

Thanks Externet..

What I understand is that The circuit I attached will use audio input which is about (0.3-3.4 KHz) and this will modulate the oscillation frequency of the LC Tank circuit to the MHz band.. and For the FSK Modulator the input is a digital data (1 and 0) and then the FSK Modulator will produce output of sine wave of two frequencies (one for the "1" and the other for the "0").



If what I wrote above is right, then still the frequency of the FSK Output is low (a few KHz) and that cant be transmitted wireless, So I will use the following circuit:



but instead of the audio input i will use the FSK Sine wave Output!!

Will that combination behave correctly as I think ?!
 

Should be absolutely fine.
Depending on the modulation rate you would use, you could end up with quite a wide band signal and thus take up a lot of bandwidth in the radio band you intend to use it on but other than that - no problem.
 

Will that combination behave correctly as I think ?!
Click to expand...
It will not behave like an industry standard FSK transmitter and respectively won't be easily to decode.
 

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