1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Spark transmitter

  1. Jan 9, 2008 #1
    [SOLVED] Spark transmitter

    1. Hello, I am making this project ( a spark transmitter and a receiver), my problem are those coils below ( Lp, La, Lr). How are they connected to the circuit.


    three images are attached for the detail

    please help me

    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

    • here.GIF
      File size:
      21.6 KB
    • 1.GIF
      File size:
      2.3 KB
    • 2.GIF
      File size:
      2.2 KB
  2. jcsd
  3. Jan 9, 2008 #2
    Lp and La are most likely transformers, and it isn't a connection, rather it works on the principle of mutual induction.

    I'm not really sure what is going on with L_R.

    From the looks of it, this circuit will probably be relatively expensive to make. Do you have to know how it works?? That could also be hard for someone without much circuit experience. That's a strange transistor configuration, and I myself would have to work it out more.
  4. Jan 9, 2008 #3


    User Avatar
    Science Advisor
    Homework Helper

    Cool project! Assuming you manage to assemble this dinosaur, can you legally operate a spark gap transmitter? I suppose the frequency is low enough it's not going to interfere with anyones iPhone. Can you still get a 2N2219 transistor? And where do you get carbon microphones? Where did you find it?
  5. Jan 10, 2008 #4
    The transistors aren't problem because I can buy some from the electronics store ( I already asked if they have some, they cost not even a dollar). Getting the carbon mic is not a problem too. The only problems are those coils I marked above and the 100pf high voltage capacitor, 'ALfa electronic'(store) has 100pf capacitor but low voltage. And Mindscrape, what do you think, whats the ratio between those coils if they are transformers. In the chart about those coils (La, Lp, Lr) is typed 22 microHenries ( henries is measurement for inductors and maybe transformers, but maybe). About the T1, it clearly says it's a transformer ( automotive ignition coil, it's ratio is 1:100 ).
  6. Jan 10, 2008 #5
    what's the ratio of the transformers?
  7. Jan 17, 2008 #6
    Sorry I didn't get back to you. I could be wrong about the La, Lp, and Lr being transformers. Lr is definitely confusing. If they are, in fact, transformers you could presumably figure out their ratios by working backwards from the definition of inductance.

    Berkman might know better, he is pretty good with circuits. If you still haven't figured it out, and need help really bad I could ask some people I personally know.
  8. Jan 17, 2008 #7
    Mindscrape, I'm so thankful for your attempts to help, anyway, I solved this problem already, and if you are interested I would upload the solution here. La, Lp, and Lr are some kind of transformers as you said, their primary and secondary windings are one above the other with a thin insulator between them and no core ( like in the Tesla coil, you should wind it by hand usually).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook