Wavelength 101
At the heart of ham radio lies a simple but powerful relationship: frequency and wavelength are two sides of the same coin. Understanding them helps you choose the right antenna, band, and mode for the kind of communication you want to do.
Let’s break this down using everyday analogies, real-world ham bands, and memorable visuals.
Basic Definitions
Frequency (f) = How many times a wave cycles in one second, measured in hertz (Hz).
Higher frequency = more wave cycles per second
Wavelength (λ) = The physical length of one full wave cycle, usually measured in meters.
Lower frequency = longer wavelength
They are inversely related by this simple equation:
Wavelength (in meters) = 300 / Frequency (in MHz)
Note: This is because the speed of light is approximately 300,000,000 m/s and MHz measures frequency in the millions.
analogy 1: guitar strings
Think of:
A thick, low guitar string = low frequency, long wavelength
A thin, high guitar string = high frequency, short wavelength
Just like strings vibrate faster or slower depending on their length and tension, radio waves do the same across the spectrum.
Watch the video below from Brotheroff to see the analogy in action:
analogy 2: Water Ripples
Drop a rock in a pond:
A big slow ripple = long wavelength, low frequency
A small fast ripple = short wavelength, high frequency
The waves are the same type (ripples), but their size and speed change how they travel.
Watch the video below from IRIS Earthquake Science to see the analogy in action:
Analogy 3: Light Spectrum
Light is also an electromagnetic wave:
Red light has a longer wavelength (lower frequency)
Blue/violet light has a shorter wavelength (higher frequency)
Ham radio waves are the same kind of wave, just much longer and slower.
Watch the video below from Colm Kelleher on how we see color to see the analogy in action:
Ham Band Examples
|
Band Name |
Frequency |
Wavelength | Notes |
|---|---|---|---|
|
70 centimeters
|
420-450 MHz
|
~0.7m | UHF; more building penetrations, shorter range |
| 2 meteres |
144-148 MHz
|
~2m | Great for local VHF comms; repeaters |
| 10 meters | 28,000-29,000 MHz | ~10m | Good for beginners during solar activity |
| 20 meters | 14,000-14,350 MHz | ~20m | Popular HF band for long=distance (DX) |
| 40 meters | 7,000-7,300 MHz | ~40m | Excellent night time band |
Practical Takeaways for Hams
Your antenna should ideally match the wavelength (or a fraction of it) for efficient transmission.
Higher frequencies (UHF/VHF) are better for short-range, line-of-sight communication.
Lower frequencies (HF bands) bend around the earth or bounce off the ionosphere for long-distance (DX) communication.
Some antennas are designed to work across multiple bands by using traps, tuners, or special matching techniques.
Quick Wavelength Calculator (In Your Head)
Divide 300 by the frequency in MHz:
300 ÷ 150 MHz = 2 meters
300 ÷ 30 MHz = 10 meters
300 ÷ 14 MHz = ~21 meters
(You can even memorize common ones!)
Summary
Frequency = how fast the wave vibrates
Wavelength = how long one wave cycle is
They're inversely linked — one goes up, the other goes down
In ham radio, this relationship affects how far your signal travels and what kind of gear you need.