Design a FM tranmitter step by step (advanced questions)

  • Thread starter yy.toh
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  • #1
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Main Question or Discussion Point

Guys, from circuitstoday.com I researched, I understood ig picture of a basic FM transmitter. there should have basic blocks like audio amp, modulator (oscillator included), radio amp and the anttena. suppose I want to build a FM transmitter, what is my first step?

step1
says I choose 0.5m long copper wire anttena, diameter to be determined, and want to have a tranmission length of 1m, what parameter is to be tuned at the anttena?can you provide the anttena formula as complete as you can-is it material dependent?how to caculate the power to be transmitted?

step 2
after I understodd the power to be transmitted, I may define the output power from radio amp, right?can someone tell me how to decide/calculate the capacitance of the ac decoupling?

step3
now come to the part of oscillator, says I use a LC osciallator the frequencies could be determined right?the connection of the LC oscillator, it should be connected before the node of ouput resistor of the transistor or after?how do we determine the value of the feedback capacitor connected to the osicillator

step4
about amplifier in general, based on what we determine the biasing resistor value, is it refering the amplifier spec for its specify Veb, Vcb?

great thanks...
and for sharing, designing a remote control is easy as just to combine the encoder/decoder with the trasceiver, so the key knowledge is to learn up the RF circuits and then the RC would be easy, just for sharing...

someone reply me please...
please...
 

Answers and Replies

  • #2
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yy.toh,

I think before the "advanced questions" can be addressed, you should probably reference the schematic you are referring to, for instance is it this one:

http://www.circuitstoday.com/medium-power-fm-transmitter-circuit

Toward the end of your post you make reference to a "remote control", is this the actual purpose of the device?

I do not have much experience with RF Transmitters/Receivers personally, but many here do; if you want help you will need to give them a specific schematic to look at before asking questions about components and parameters. What little experience I have with RF circuits is that very small details can have a large impact on performance. Additionally, defining the specific purpose of the circuit will go a long way to getting good advise.

Fish
 

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