The Sierra 303B debuted circa 1974, covers a frequency range of 9 kHz–3.3 MHz, has AM/LSB/USB mode selection, a large (4 in. x 3 in.) signal meter that’s internally calibratable, selectable input ...

So [Todd] has set out to build an Arduino frequency counter for a Kenwood TS-520S HF ham radio. This post (and the video found after the break) doesn’t cover the entire project.