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Schematic Symbol Help? (SuperSID)

  1. Sep 7, 2013 #1
    Hi, can anyone help me identify the big blue boxes' schematic symbol? The actual physical component sort of looks like a small inductor or oscillator.

    SuperSID Schematic

    The purpose of this circuit is to be a preamplifier for VLF signals related to ionospheric disturbances, I believe.
     
  2. jcsd
  3. Sep 7, 2013 #2

    FOIWATER

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    It's the symbol for a varistor, I assume it's for attenuating (resistor) transients and shunting (the varistor) transients. A surge protecting device?

    My best guess, might not be correct though
     
  4. Sep 7, 2013 #3
    Ok, that actually makes sense, the antenna I have connected will get big spikes from CRT monitors and even fluorescent lights if close enough. Probably some other stuff can cause bigger problems.
     
  5. Sep 7, 2013 #4

    dlgoff

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    Last edited by a moderator: May 6, 2017
  6. Sep 7, 2013 #5
    Hmm, ok...so its kind of like a reusable fuse here? Like it opens a path to ground if current (thus temperature) gets to high? Sorry, I don't know much about electronics.
     
  7. Sep 7, 2013 #6

    dlgoff

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    I don't know what the A inputs are, but it looks like it's used as a temperature sensor to adjust for temperatures differences. (varying temperatures outdoors perhaps?)

    From the http://en.wikipedia.org/wiki/Thermistor link.

     
  8. Sep 7, 2013 #7
    The A's are the antenna connections. It's a 1m "small loop" (primarily detects magnetic component of EM radiation) antenna suitable for detecting the transmitted VLF radio signals that are part of submarine communication networks.

    The idea is that when a solar flare occurs, the ionosphere is disturbed which also disturbs this network. SID is sudden ionospheric disturbance; this is the second (super) version of a circuit developed by Stanford for mass distribution to high schools for the purpose of space weather education.
     
  9. Sep 7, 2013 #8

    dlgoff

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    Outstanding. What a fun way to learn. :thumbs:
     
  10. Sep 7, 2013 #9
    Yes they had a lot of fun building the antenna and seeing the response of fluorescent lights and a CRT tv, and trying to find the VLF stations. I just wish I knew more about the circuit so I could I could explain it to them, heh. I understand at a basic level the circuit is just a preamp, and understand opamps somewhat, but that is about it.
     
  11. Sep 8, 2013 #10

    jim hardy

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    They're clearly surge suppressors, one for normal mode and one common mode.

    A 1 m^2 loop doesn't sound big, but nearby lightning strokes generate substantial electro-magnetic fields.
    I once returned from a vacation to find in my garage:

    In my FM receiver two capacitor-looking devices that coupled the antenna leads were blown apart; they might have been suppressors I don't know for the receiver still worked but sensitivity was degraded.

    My two magnetic compasses that i kept near the workbench had got their needles re-magnetized so the red ends pointed south instead of north.

    I suspect this circuit designer has a similar experience under his belt...
     
  12. Sep 8, 2013 #11

    dlgoff

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    Thanks for the correction Jim.
     
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