Project: Wide Range 12 - 40 MHz HF Synthesizer



Design Services Performed:


This synthesizer was designed to drive a high performance HF (Shortwave Receiver) receiver, but it has applications to any HF radio in the DC to 50 MHz band. Low phase noise and reference feedthrough were also design goals. The design is fully self contained and utilized a low cost shielding arrangement that eliminated the need for costly custom shields. Using a clever AC CMOS gating arrangement the 50 - 100 MHz VCO is divided and filtered to cover the full 12 - 40 MHz range. A PIC Microcontroller controls the programming and reads a panel mounted rotary encoder and drives a Vacuum Fluorescent Display (VFD). Power is provided from a simple UL approved Wall Wart power supply. A low cost double sided board was utilized to keep manufacturing costs down.

  • Low cost and high performance by using standard RF parts, clever use of AC CMOS and standard mechanical enclosures.
  • Fully self contained with PIC Microcontroller driving a VFD display.
  • Single supply operation.
  • Reference spur suppression > 85 dBc.
  • Harmonics > 40 dB down.
  • Phase noise of 122 dBc / Hz at 10 kHz offset.
  • 11 dBm output power.
  • Self contained low noise, low drift, crystal reference oscillator.
  • RF and PSpice simulations used to verify and optimize the VCO design.

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