We have a project to design a wireless full duplex intercom circuit using frequency modulation technique. I've searched the web for designs and I have come up with these:

Low Power FM Transmitter Low Power FM Transmitter

Simple FM Receiver Simple FM Receiver

Our plan is to create two pairs of transmitters and receivers, tuning the trimmer capacitor to a blank channel (says on each design that it should transmit/receive between 88 MHz to 108 MHz), each with different center frequencies (one pair could be tuned to 100.5 MHz and another to 93.5 MHz, for example)

So our questions are these.

  1. What is the L2, C6, and C7 for? (Transmitter)
  2. What would be the transmitting range of the transmitter?
  3. Would my plan work?
  4. Any tips to improve the design?
  • 3
    I hope that you realize that, depending on your country's regulations, you're not allowed to transmit in the 88 - 108 MHz band. These designs are extremely simple and will have disappointing performance. It might be that your usable range is only a couple of meters in open space. If you have to ask what certain components are for, then I doubt that you have enough experience to make these circuits work. – Bimpelrekkie Oct 11 at 12:25
  • 1
    You probably won't have much fun with those. The transmit and receive frequencies won't be very stable You'll spend most of your time tuning one or the other to keep them on the same frequency. As for range: Too short with that receiver, probably long enough to get you in trouble with that transmitter. – JRE Oct 11 at 14:51
  • You are aiming for the top rung of the ladder but your circuit design is close to the bottom rung. You have several more rungs to climb (learning design and regulations and specification writing) before this question can be reasonably answered on this site. – Andy aka Oct 11 at 18:17

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