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Resonant Frequency and the Slide Rule...

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  • wobbly127
    This is an operation i do quite a bit, homebrewing regenerative receivers. Here is my method: to find the tuning range for a 30-365 picofarad capacitor and a
    Message 1 of 1 , Jan 7, 2004
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      This is an operation i do quite a bit, homebrewing regenerative
      receivers.

      Here is my method:
      to find the tuning range for a 30-365 picofarad capacitor and a 240
      microhenry inductor.

      Let me do it two ways, one for use on a slide rule with a mannheim
      layout, one for a Doric arrangement. (on the mannheim, i often make a
      gauge mark at 2Pi on the CI scale... then it all works out like the
      doric arrangement.)

      Lets find the low frequency range on the mannheim.

      Set left A index to 240, set cursor at 365 on B. Because this is 3+3
      digits (even) use the leftmost pair. (roughly 8.78) (See note).
      Line up the 2 on the CI scale on the cursor, and then move the cursor
      to the PI on the C scale. (*2 *pi) (Roughly 1.86)
      Index on C, read resonant frequency on C opposite index on D. Answer
      is 537 KHz.

      Note: This is easier if you have a gauge mark at 2PI on CI or have a
      CIF scale. Simply line up the 2PI (2 on CIF) with the answer from
      step 1, and read the resonant frequency off at the D index.

      Thus:

      High resonant frequency:

      Left A index at 240, set cursor at 50. (this is 3+2 digits, so use
      right hand pair)set cursor there (roughly 8.5 on D).

      Line up the 2PI gauge mark or the 2 on CIF at the cursor, read 1.873
      MHz on C above D index.

      This does not work nearly as well on my N4 with no A-B scales, i wind
      up having to read the root and placing it on the C-D scales.


      Regards,

      Ed
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