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STEP 02 / 06 · ABOUT 5 MIN

Connect frequency and wavelength

MHz describe cycles per second; metres describe the spatial length of a wave.

Frequency is the number of cycles per second. 1 MHz equals 1,000,000 Hz. Free-space wavelength is λ = c / f. Using c ≈ 300,000,000 m/s gives the practical approximation: wavelength in metres ≈ 300 / frequency in MHz.

At 145 MHz this is about 2.07 m; at 435 MHz about 0.69 m. Three times the frequency means one third of the wavelength. This is not yet a finished antenna length: design, surroundings and shortening affect a practical antenna. Propagation in cable is slower than in free space.

Your turn.

Open the wavelength calculator. Calculate 145 MHz, then 435 MHz. Compare the wavelengths and return using the learning path link to answer the check.

Try it: wavelength calculator →Read more: frequency and wavelength →
UNDERSTAND & APPLY

Check your understanding

You triple the frequency. What happens to free-space wavelength?

Sources & further documentation

Your learning path— / 6
  1. Understand the receive chain
  2. Connect frequency and wavelength
  3. Read the waterfall
  4. Match mode and filter
  5. Use gain deliberately
  6. Tune your own signal

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