Building a discrete/analog FM walkietalkie

Discussion in 'Wireless & RF Design' started by oveee92, Aug 9, 2014.

  1. oveee92

    Thread Starter New Member

    Aug 9, 2014
    2
    0
    Hi! Im new to this forum, and hope I can get some help with my potential project :)

    I study in an electro/radio/telematics engineer university, and after building a simple 27 MHz RF transmitter last year (http://www.pyroelectro.com/projects/pyro_rf_transmitter_27mhz/index.html), my classmate and I decided to bring it one step further.
    Our dorms are about 15 meters and one floor apart, and in the spirit of laziness, we want to make a pair of simple walkies to communicate! They do not need a lot of tx effect, and do not really have to be portable either!

    Since we would like to study how it actually works, we decided to only use discrete/analog components (no ICs), and since we are fine with using half duplex, we might just use the same frequency for both transmitters and receivers, and just make two of them!
    We consider just using the same antenna and power source for both the transmitter and receiver circuits, switching between them by keying a button. (is this even practical?)

    It's not easy to find such a circuit online, but i found two that might do, and tried to combine them. I hope I can get some input on whether this will work!
    circuit1.png
    my source for these circuits is here: http://myfreetimehobbies.blogspot.no/2012/08/simple-fm-walkie-talkie_11.html
    Note that all of the inductors are 1mH, because they all seem to be made by twisting insulated copper, and I haven't found a value for them yet :)

    As you can probably see, this is a bit of a cluster, do you guys have any idea how I can make it simpler? I'm completely open for improvements! I have access to an electro lab, and can also order components from ELFA or Farnell if I need.

    also note, I have learned the theory behind all the concepts neccesary to make this, but as we know, circuit configurations are pretty diverse, and I do not have much experience with practical electronics! So I might seem a bit slow, but don't be afraid to use difficult terms and circuits, I'm a quick learner :)

    Thanks in advance! :D
     
  2. BeerBelly

    New Member

    Dec 16, 2013
    29
    5
    . ICs have become the basic building blocks of todays circuits. I've been working with electronics for better than 50 years yet I still wouldn't want the fustration of using only transistors to build a transceiver. Audio amp ICs., OP amps,PLL detectors, are easier to understand and alot more stable in this type of application.
    . If you are bent on using transistors , then build the transmitter and use a portable radio for a receiver.
    .
    Just my 2 cents.
     
  3. BeerBelly

    New Member

    Dec 16, 2013
    29
    5
    By the way.
    Welcome to the forum and let us know how it turns out.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    you have already built a transmitter, just build a reciever to go with it and the switching circuits.
     
  5. oveee92

    Thread Starter New Member

    Aug 9, 2014
    2
    0
    thanks for replying :)
    so i have been able to pretty much fully understand how the transmitter part works, but is the receiver so much more difficult?

    half the reason i want to build this is to understand how it works on a very low level, so unless it will take months i would still like to avoid ICs :)
     
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