Designing FM Transmitters: Tips and Techniques for Selecting Component Values

In summary, you want to know how to design a coil to resonate with a specific capacitance and frequency. There is a formula for doing this and it can be found online. You would need a small coil and a crystal to make it work.
  • #1
okwatia
15
0
I want to know how to design fm transmitters. That is how to select appropriate values of the components. I need help
 
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  • #2
This is a really, really broad question. Also, it should be in the Electrical Engineering or regular Engineering subforums. Since you're asking about specific component values, do you have a design that you're already using?
 
  • #3
goto this site
http://knowhowstuff.blogspot.com/2009/05/fm-transmitter.html
 
  • #4
Hello;
I want to know only how to make a coil for specific output frequency? what is a crystal? How to make a crystal and how to use it?
 
  • #5
There is a formula for designing tuned circuits.

L (inductance of coil in microhenries) = 25330.3 / ((Frequency in MHz) * (Frequency in MHz) * (Capacitance in pF))

So, to make a coil to resonate with 50 pF at 25 MHz you would need an inductance of 0.81 microhenries.
In practice, this would be a small coil maybe 10 mm in diameter with 6 turns of wire on it and you might make the capacitor partly variable to tune the circuit and achieve resonance.

There are many inductance calculators on Google. They usually give different results for small coils but better ones for larger coils.

Regarding crystals... you always have to buy these. There are large factories that make them but you would not be able to make them at home. Old computers always have a few crystal oscillators in them.

See the following site for quite a good article about quartz crystal oscillators.
http://en.wikipedia.org/wiki/Crystal_oscillator
 
  • #6
It not really possible to wideband FM a crystal oscillator. Free running oscillators will FM easily but do drift. It is possible to have a phase locked loop which holds the centre frequency steady but allows deviation. Some broadcast FM transmitters deviate a stabilised 10.7 Osc (required to remain within a few hundred Hz by the authorities) and then mix up to the final frequency.
 

1. How does an FM transmitter work?

An FM transmitter works by converting an audio signal into radio waves through a process called modulation. The audio signal is used to vary the frequency of the radio wave, creating the characteristic "FM" sound. The transmitter then amplifies the signal and sends it out through an antenna.

2. What components are needed to design an FM transmitter?

The main components of an FM transmitter include an oscillator circuit, a modulator circuit, an amplifier, and an antenna. Some designs may also include a frequency multiplier or a frequency mixer to improve the quality of the transmitted signal.

3. How can I improve the range of my FM transmitter?

To improve the range of an FM transmitter, you can use a higher quality antenna, increase the power of the amplifier, and optimize the modulation and filtering circuits. It is also important to choose a clear and unoccupied frequency for your transmitter to minimize interference.

4. What are the legal considerations for designing an FM transmitter?

In most countries, the use of FM transmitters is regulated by government agencies. It is important to research and adhere to the laws and regulations in your area, such as obtaining a license or staying within certain power limits. Failure to comply with these regulations can result in fines or legal action.

5. Are there any safety precautions I should take when designing an FM transmitter?

Yes, it is important to follow safety guidelines when designing an FM transmitter. This includes using appropriate shielding and grounding techniques to prevent electric shocks and interference. It is also important to avoid using high voltages or currents that could cause damage or harm to yourself or others.

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