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old nomenclature for capacitance

Discussion in 'Electronic Basics' started by Martin Baker, Dec 9, 2003.

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  1. Martin Baker

    Martin Baker Guest

    Dear Group,
    I am trying to help restore an old amplifier, and we have a
    schematic, but it shows capacitances in mmf. If I were to guess, I
    would probably think it meant millmicrofarads, or nanofarads, but it
    could mean something entirely different.

    Does anyon know exactly what a mmf is?

    Thanks in advance,

    Martin
     

  2. It's "micro-micro-farad". I have no idea where the terminology
    originated, but it's the same thing as pF. So 10uuF is 10pF.

    Michael
     
  3. DarkMatter

    DarkMatter Guest


    If this is true, that particular cap would be in quite a small
    package.

    If he is referring to designations on an electrolytic cap, then your
    assessment must be incorrect. I do not know of any picofarad
    electrolytics.
     
  4. You've just showed your age.

    All you have to do is look at any book beyond a certain age, and
    you will see uuF used for pF.

    I just pulled one out, from 1958, and I opened it at random.
    Right away, a 28 to 50Mc oscillator. A 75uuF variable. The feedback
    capacitor is 10uuF. There is no way those are electrolytic.

    Clearly, either they are small capacitors, feedback capacitors maybe,
    or the original schematic is at fault.

    I wasn't guessing; the useage fell out of favor in the early sixties,
    which was before my time, but in any of the old books I collected
    thirty years ago it was a common useage.

    You aren't familiar with the term, yet you dismiss my explanation
    because it isn't what you expect.

    Michael
     
  5. Rich Grise

    Rich Grise Guest

    Yes they're micromicrofarads, but that's a picofarad.
    A nanofarad is a millimicrofarad.

    Cheers!
    Rich
     
  6. Rich Grise

    Rich Grise Guest

    It's because it wasn't until the early '60s or whatever
    that the term "picofarad" was invented.

    I remember looking at one of the Heathkit scopes from
    that era and wondering "what the hell is a nsec?" Then
    we found out that it was "nano-," and of course, they
    immediately became bananaseconds. %-}

    cheers!
    Rich
     
  7. Hi,

    Back when Roosevelt ruled the roost, some American schematics
    used 'M' for 'k', i.e. 10k was marked 10M, and in the 'Admiralty
    Handbook of Wireless Telegraphy - 1938' (Royal Navy) all the
    capacitances are quoted in 'Jars', which I believe is about 900
    pf.

    And they're still dreamin' in California about the mmf's and
    the pf's :)


    Cheers - Joe
     
  8. John Larkin

    John Larkin Guest

    It used to be a millimicrosecond.


    John
     
  9. Ross Mac

    Ross Mac Guest

    You are correct!...I remember that nomenclature from my early days in the
    business....pf was a fairly new entitiy back then.....Happy Holidays....Ross
     
  10. Ross Mac

    Ross Mac Guest

    That too is correct...it's all about exponential notation...
    In the days of the slide rule...it was particularly important...It was the
    only way to keep track of the decimal point!
    I still have my Pickett stuffed away in a case...Anyone else save their
    slide rule out there?......take care, Ross
     
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