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how does this work??

Discussion in 'General Electronics' started by jeff, Aug 9, 2003.

  1. jeff

    jeff Guest

  2. no_one

    no_one Guest

    part of a tuned "tank" or rlc circuit?
     
  3. Rich Grise

    Rich Grise Guest

    Yes, and yes. Actually, tha cap's leads are the antenna - sort of
    a loaded half-folded-dipole, ... nah! it's just a quarter-wave whip.
    The cap value is irrelevant. The 1458 does the detecting with the
    e-b junctions of the input transistors. And it's clearly adjustable:

    -----------------------------<quote>-----------------------------
    .... R5 sets the switching threshold of the second op-amp; normally it
    is adjusted so that the circuit barely triggers on background noise,
    then it's backed off a bit. The response of the circuit may be tuned
    by adjusting the length of the leads on C1. For typical road-radar
    systems, the input capacitor's leads should be about 0.5 to 0.6 inches
    long.
    ------------------------------</quote>-----------------------------

    So R5 adjusts the sensitivity, and the length of C1's leads set the
    frequency.

    Cheers!
    Rich
     
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