Colpitts Crystal Oscillator

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CP-OSC BNC Rev2-720px.jpg

Features[edit]

  • Colpitts Crystal Oscillator
  • Useful for binning crystals for use in building crystal filters
    • Hand select close crystal frequency values from a pile of 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
    • 18 mA at 14V

Schematic[edit]

CP Osc Schematic Rev2.PNG]

Tested With[edit]

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

Prototype[edit]

Colpitts Osc P1780-720px.jpg

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

XTAL-Osc-5-720px.jpg

Scope Caps[edit]

  • UUT = 4.4433 MHz crystal
  • 8 Digits Frequency Counter shows 4.432285 MHz
  • Rigol DS1054Z - 50 MHz scope (100 MHz mod)
  • UltraScope
  • Waveform triangular

Prototype[edit]

XTAL-Osc-UltraScope-01.PNG

SMT Build[edit]

CP Osc 4p43MHz Rigol HiZ In.png]

tinySA Measurements of SMT Build[edit]

SMT build - Rev 1[edit]

  • 12V power
  • 4.43 MHz crystal
  • Measured +8.6 dBm into 50 ohm load
  • 40 dBm attenuator to protect tinySA
  • 8 Digits Frequency Counter shows 4.432298 MHz

CP Osc 4p43MHz SMT tinySA.PNG

  • 4 to 30 MHz scan
  • Rich even and odd harmonic content
  • -60 dBm down outside of harmonics

CP Osc 4p43MHz 4 to 30MHz SMT tinySA.PNG

  • 4 to 100 MHz

CP Osc 4p43MHz 4 to 100MHz SMT tinySA.PNG

  • 5V Operation
  • +4.3 dBm

CP Osc 4p43MHz 4 to 10MHz 5V SMT tinySA.PNG

SMT build - Rev 2[edit]

CP-OSC BNC Rev2-720px.jpg

  • 12V power
  • 4.43 MHz crystal
  • Measured +7.56 dBm into 50 ohm load
  • 20 dBm attenuator to protect tinySA
  • BNC connector

CP Osc 4p43MHz 4 to 30MHz SMT BNC Rev2 tinySA.PNG

  • SMA connector

CP-OSC SMA Rev2-720px.jpg

CP Osc 4p43MHz 4 to 30MHz SMT SMA Rev2 tinySA.PNG

W2AEW Video[edit]

  • Wes Haywood EMiRFD circuit

XTAL-Osc.PNG

XTAL-Osc-2.PNG

XTAL-Osc-3.PNG

Assembly Sheet[edit]

Colpitts XTAL Oscillator Rev 1 Assembly Sheet

Colpitts XTAL Oscillator Rev 2 Assembly Sheet