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14233Re: Crystals & Oscllators [Maybe more than you wanted to know]

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  • Claudio Re
    Sep 2, 2007
      Thanks a lot Dick !
      What a nice and huge docs to digest ....!
      Some documents are in frames and I was not able to download them
      totally .
      Any suggestions ?
      CLaudio I1RFQ

      --- In softrock40@yahoogroups.com, "dick_faust" <dick_faust@...>
      > I was going to write something, but the following references do a
      > much better job at teaching and answering many of the questions
      > recently posted.
      > Quartz Crystal Resonators and Oscillators for Frequency Control
      > Timing Applications - A Tutorial, by John R. Vig [3 formats]
      > http://www.ieee-uffc.org/freqcontrol/VigBallato/fcdevices.PDF
      > http://www.ieee-
      > uffc.org/freqcontrol/tutorials/vig2/tutorial2_files/frame.htm
      > http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3.ppt
      > The Fundamental Theory of Low Noise Oscillators with Special
      > Reference to Some Detailed Designs, by J. Everard
      > http://www.ieee-uffc.org/freqcontrol/tutorials/FCS%20Tutorials%
      > 2000/everard.pdf
      > Low Noise Oscillator Design and Performance, by Michael M. Driscoll
      > http://www.ieee-
      > uffc.org/freqcontrol/tutorials/2002_IEEE_Tutorial_files/frame.htm
      > Clock Jitter, by R. Temple
      > http://www.ieee-uffc.org/freqcontrol/tutorials/FCS%20Tutorials%
      > 2000/Temple_files/frame.htm
      > Now my addition is limited to some crystal specifications & notes
      > apply to the 20/30M daughter board.
      > The crystal should be specified as a fundamental series resonate
      > device at what ever make tolerance desired. Note: the Butler
      > oscillator operates on the fundamental frequency which is slightly
      > different than 3rd overtone. I have no idea what drive level is
      > present, but stay in HC-49 case, if at all possible, as this is
      > largest quartz blank.
      > The Butler oscillator uses the "tuned" tank circuit to extract the
      > third harmonic and provide the balance of the phase shift and gain
      > required to sustain oscillation. The "tuned" circuit needs to
      > resonate higher than the third harmonic to meet the operating
      > conditions and usually is not critical [often why swamped with a
      > resistor]. The circuit will also work with a fundamental crystal
      > at a higher crystal drive current. In both cases the actual
      > operating frequency will be somewhat higher than the actual series
      > resonant frequency. So use a frequency counter [or radio] to
      > determine the exact frequency.
      > The series resonant frequency of a crystal is always lower than
      > parallel resonant frequency. Parallel resonant crystals are
      > correlated with an external parallel capacitor across the crystal,
      > usually 18pF, 20pF or 32pF. The higher the external cap, the
      > the anti-resonant [parallel resonant] frequency will be.
      > always operate between the series and loaded anti-resonant
      > frequencies. [Exception: If there is an external inductor, it
      > move the series resonant frequency lower]
      > It is quite simple to measure the two frequencies of a crystal
      > minimum equipment. A stable 50 ohm signal generator or DDS and a
      > meter [a receiver, RF Voltmeter or an rf probe if you have a large
      > enough signal]. Take 2 resistors from 1K to 10K and connect
      > in series. Connect one end to the generator and the other to the
      > meter. Connect one lead of the crystal at the center and the
      > to the shields [gnd] of the generator and meter. As you manually
      > sweep the generator through the series resonant frequency of the
      > crystal there will be an 80 to 100 db drop in amplitude about 5Hz
      > wide at the series resonant frequency - so go slow. If you put
      > crystal in series with the resistors the same effect will be
      > at a somewhat higher frequency when the elements are parallel
      > resonant and block the signal. A 20pF cap in parallel with the
      > crystal will lower the frequency to the 20pF correlation
      > The resistors serve to isolate the external strays and give very
      > reliable readings. The anti-resonant null is much broader than
      > series resonant due to the effects of circuit Q.
      > A final reference that may be found in Amateur publications is :
      > DEMPHANO, A device for measuring phase noise, Communications
      > Quarterly, Spring, 1999, pp. 9-17 by J. Makhinson – cq199904.pdf
      > Dick Faust
      > K9IVB
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