VFO-001

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VFO-001 P132-720px.jpg

Features[edit]

Schematic[edit]

VFO-001-SCHEMATIC-V2A.PNG

  • PWR* - connect only when no Mini-360 Buck Regulator is used
  • PD01 - Power Distribution card (not shown)

Build[edit]

  • BNC/Power Jack placement

VFO-001-Nibbler-BNCs Placement-720px.jpg

  • Rear panel BNCs and power jack

VFO-001-Rear Panel-720px.jpg

  • Drill holes and nibble out for OLED cutout
    • A bit rough
    • Better to undercut nibble and file to size

VFO-001-Nibbler-01-720px.jpg

  • OLED fitted

VFO-001-Nibbler-OLED-Fitted-720px.jpg

  • Final

VFO-001 P132-720px.jpg

Libraries/Example Code[edit]

Land Boards Code[edit]

VFO Menu[edit]

  • Set Step Size
    • 1Hz, 10 Hz, 100 Hz, 1KHz, 10KHz, 100 KHz, 1 MHz, 10 MHz
  • Set frequency
    • 10 KHz to 40 MHz in step size steps
  • Select VFO
    • VFO0, VFO1, VFO2
  • VFO On/Off
    • On, Off
  • Drive Level
    • 2 mA, 4 mA, 6 mA, 8 mA
  • Set Calibration Value
    • In step size steps (down to 1 Hz)
  • Save (power-on) defaults

Libraries used in this app[edit]

Other Si5351 Libraries[edit]

Calbration Using WWV[edit]

  • Good method that doesn't require a frequency counter
  • Tune via ear and S meter
  • Requires shortwave (or ham) receiver that can receive 5/10/15 MHz
  • Rough tune calibration factor on scope or frequency counter
  • Fine tune to 1 Hz using WWV
  • 15 MHz WWV midday has better resolution

Output Drive Level[edit]

  • First, calculate the "theoretical" drive level and then measure the actual drive level into a 50 ohm load

Si5351A Drive Level[edit]

  • Si5351A drives 3.3V square waves
  • Si5351A datasheet lists 50 Ohm source impedance
    • Half of the power would be dissipated in the source and half in a 50 ohm load
  • The RMS value for square-wave voltages whose pulse duration (ti) and pause (tp) have the same length:

RMS-SquareWave.PNG

RMS-SquareWave-2.PNG

  • Using a "theoretical" drive level of 3.3V

Si5351 Drive-Level dBm.PNG

  • 54 mW is 17.3 dBm total power
  • Half delivered to load = 27 mW
    • 14.3 dBm "theoretical" drive level
  • ADE-1 needs +7 dBm drive level
  • Would in theory need a 7 dB attenuator between the Si5351A and the ADE-1
  • Reality, the output drive in the Si5351A is controlled by the output drive control register
  • Si5351A outputs as measured with tinySA
    • Drive Level 2 mA = 0.2 dBm
    • Drive Level 4 mA = 6.2 dBm < Best choice for driving +7 dBm mixers like the ADE-1
    • Drive Level 6 mA = 9.7 dBm
    • Drive Level 8 mA = 11.7 dBm

Measured[edit]

  • Channel CLK0
  • 10 Mhz
  • 30 dB external attenuator (gain set in tinySA to -30dB)
  • Output level at 2 mA
  • Scan 1MHz to 300MHz

TinySA VFO-001 10MHz-Signal 1MHz-to-300MHz.png

  • Zoom into 10 MHz fundamental
  • Approx. 1 dBm signal level

TinySA VFO-001 10MHz-Signal Narrow-10MHz.png

Videos[edit]