Radio Theory

Sub-topics

• Frequency & Wavelength

  Electromagnetic waves, the 300/f relationship, bands and harmonics.

• Modulation & Emission Modes

  AM, FM, SSB, CW and digital modes, plus the bandwidth each occupies.

• Transmitters & Receivers

  Oscillators, mixers, superheterodyne stages, sensitivity, selectivity and squelch.

Lessons

• Frequency, wavelength and why bands have names

  The 300 ÷ f shortcut, where band names like '2 metres' come from, and how harmonics get you into trouble.

  6 min

• Modulation modes compared

  AM, FM, SSB and CW — what each one varies, how much bandwidth it needs, and when you would choose it.

  7 min

• How a superheterodyne receiver works

  Mixers, the intermediate frequency, why the design won, and what sensitivity, selectivity, AGC and squelch each mean.

  8 min