Colpitts Crystal Oscillator

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Colpitts Osc P1780-720px.jpg

Features[edit]

  • Colpitts Crystal Oscillator
  • Useful for binning crystals
  • Made from junk box parts
    • (2) 2N3904 transistors
    • Standard value 1/4W resistors
  • Design from Experimental Methods in RF Design - Fig 7.69
    • Built by others (W2AEW, IMSAIGuy, etc)
  • Runs from 4V to >16V
    • May run at higher voltages, didn't tempt fate
  • 15mA with 4.44 MHz crystal at 12V

Tested With[edit]

  • 4.433 MHz crystal - worked
  • 16 MHz crystal - worked
  • 27 MHz crystal - didn't work

Prototype[edit]

  • Cut square PCB material for raised pads
  • Build on single side Copper clad PCB material
  • Large ground plane

XTAL-Osc-5-720px.jpg

Prototype Scope Caps[edit]

UUT = 4.4433 MHz crystal[edit]

XTAL-Osc-UltraScope-01.PNG

  • FFT
  • 0-50 MHz
  • Shows lots of extra noise
    • In plastic box

XTAL-Osc-FFT-01.PNG

  • Fundamental - zoomed in

XTAL-Osc-FFT-03-Findamental.PNG

  • FFT 3rd harmonic
    • 3rd harmonic down about 20 dB

XTAL-Osc-FFT-02-3rdHarmonic.PNG

UUT = 16.000 MHz crystal[edit]

  • Sinewave is cleaner

XTAL-Osc-UltraScope-02-16MHz.PNG

XTAL-Osc-FFT-06 16MHz.PNG

W2AEW Video[edit]

  • Wes Haywood EMiRFD cirvuit

XTAL-Osc.PNG

XTAL-Osc-2.PNG

XTAL-Osc-3.PNG

PCB[edit]

CP-OSC-3D-3.png

Assembly Sheet[edit]

Colpitts XTAL Oscillator Rev 1 Assembly Sheet