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Tuning Cap Pfd Question

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  • patrick_mcstorm
    Hello Would it be a valid statement to say, (with the exception really old schematics from the days of micromicrofarads) that picofarad (pFd -or- pF) is the
    Message 1 of 8 , Jul 9, 2014
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      Hello


      Would it be a valid statement to say, (with the exception really old schematics from the days of micromicrofarads) that "picofarad" (pFd -or- pF) is the standard term when referring to tuning capacitors in modern schematics?


      Thanks


      Patrick


      p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.

      <snip>


    • John Popelish
      On 07/09/2014 09:43 PM, vw_beetle_fix_it@yahoo.com ... Yes. I guess some very large caps could exceed 1000 pF and be labeled in nF (1 nanofarad = 1000
      Message 2 of 8 , Jul 9, 2014
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        On 07/09/2014 09:43 PM, vw_beetle_fix_it@...
        [Electronics_101] wrote:

        > Would it be a valid statement to say, (with the exception
        > really old schematics from the days of micromicrofarads)
        > that "picofarad" (pFd -or- pF) is the standard term when
        > referring to tuning capacitors in modern schematics?

        Yes. I guess some very large caps could exceed 1000 pF and
        be labeled in nF (1 nanofarad = 1000 picofarad), but I have
        never seen one.

        --
        Regards,

        John Popelish
      • Andy
        I think what you are asking is: If you see a schematic that has the values printed next to the tuning capacitors, but it doesn t show the units, is it safe to
        Message 3 of 8 , Jul 9, 2014
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          I think what you are asking is: If you see a schematic that has the values printed next to the tuning capacitors, but it doesn't show the units, is it safe to assume that the numbers are in picofarads?

          I think the answer is: most likely yes.  But not with absolute certainty.  I think for most RF tuned circuits, they probably would be in picofarads.  But even a frequency as low as 25 kHz could be considered "RF" (for the guys who monitor those ELF transmissions), and in that case a larger capacitor might be needed.  Probably not microfarads, but maybe nanofarads (1nF = 1000pF = 0.001uF).

          I don't particularly like it when a schematic leaves things out like that.  It should say "47pF" or "47p" (or in the old days, "47mmF" or "47uuF") and not just 47.

          Regards,
          Andy


        • patrick_mcstorm
          Hello Thank you, John. Best regards Patrick p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.
          Message 4 of 8 , Jul 9, 2014
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            Hello

            Thank you, John.

            Best regards

            Patrick

            p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.
          • Andy
            And of course this assumes you really do mean the tuning capacitors, not bypass capacitors or something else ... which could have much larger capacitance
            Message 5 of 8 , Jul 9, 2014
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              And of course this assumes you really do mean the tuning capacitors, not bypass capacitors or something else ... which could have much larger capacitance (could be greater than 1uF so the value on the schematic might be in microfarads rather than picofarads).

              Andy


            • patrick_mcstorm
              Hello Thank you, too, Andy. Best regards Patrick p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.
              Message 6 of 8 , Jul 9, 2014
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                Hello

                Thank you, too, Andy.

                Best regards

                Patrick

                p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.

              • patrick_mcstorm
                Hello By the way, Andy, you are 100% correct here: I think what you are asking is: If you see a schematic that has the values printed next to the tuning
                Message 7 of 8 , Jul 9, 2014
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                  Hello

                  By the way, Andy, you are 100% correct here:

                  "I think what you are asking is: If you see a schematic that has the values printed next to the tuning capacitors, but it doesn't show the units, is it safe to assume that the numbers are in picofarads?"

                  Best regards

                  Patrick

                  p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.


                • patrick_mcstorm
                  Hello By the way, Andy #2: In chemistry, a number without (a) unit(s) is meaningless, even if the units are given somewhere else in the text as
                  Message 8 of 8 , Jul 10, 2014
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                    Hello

                    By the way, Andy #2: In chemistry, a number without (a) unit(s) is meaningless, even if the units are given somewhere else in the text as presented...though some textbooks fudge a little here and there for the space saving. The ONLY valid statement without units is the accompanying chemical equation following the text describing the reaction.

                    Chemistry students making this mistake generally do it only one time... after they find a grade of "zero" on an assignment they've turned in... expecting a grade of 100%

                    Thanks

                    Patrick

                    p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.

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