Colpitts Crystal Oscillator
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Contents
Features
- 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
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Tested With
- 4.433 MHz crystal - worked
- 16 MHz crystal - worked
- 27 MHz crystal - didn't work
Prototype
- Cut square PCB material for raised pads
- Build on single sided Copper clad PCB material
- Large ground plane
Scope Caps
- 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
SMT Build
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tinySA Measurements of SMT Build
SMT build - Rev 1
- 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
- 4 to 30 MHz scan
- Rich even and odd harmonic content
- -60 dBm down outside of harmonics
- 4 to 100 MHz
- 5V Operation
- +4.3 dBm
SMT build - Rev 2
- 12V power
- 4.43 MHz crystal
- Measured +7.56 dBm into 50 ohm load
- 20 dBm attenuator to protect tinySA
- BNC connector
- SMA connector
W2AEW Video
- Wes Haywood EMiRFD circuit
