Use the free tool above, then read on for how it works, a worked example, and practical tips.
What this tool does
Antenna books talk about height in wavelengths, not in metres, because the radiation pattern depends on height measured against the wavelength in use. This calculator converts your mast height and frequency into wavelengths, so you can compare your setup with the classic half-wave, one-wave, and two-wave heights the books recommend.
How it works
The tool finds the wavelength by dividing the speed of light, 299.792458 megametres per second, by your frequency in megahertz, giving metres. It then divides your height in metres by that wavelength, and it also shows the quarter-wave and half-wave heights at the same frequency for quick comparison.
How to use it
- Enter your values in the boxes above.
- Press the calculate or play button.
- Read the result shown below the tool.
- Try a second set of values to compare options.
Worked example
A 10-metre mast at 145 MHz sits at a wavelength of about 2.07 metres, so the mast is roughly 4.8 wavelengths high, which is a comfortable height for VHF work. The same 10 metres at 7 MHz, where the wavelength is about 42.8 metres, is only 0.23 wavelengths, which explains why low-band antennas behave so differently on the same mast.
Practical tips
When comparing masts, compare wavelengths rather than metres, because a modest mast can be electrically tall on VHF and electrically low on HF at the same time. Raising an antenna by half a wavelength often changes the pattern more than adding power, especially for low-angle DX radiation.
Common mistakes
A common mistake is entering height above sea level instead of height above local ground, which inflates the figure on a hilltop. Another is using the height of the mast base rather than the height of the radiating element itself, which is what the antenna actually sees.
Questions and answers
Is this tool free? Yes. It runs in your browser, needs no account, and gives instant results.
Do I need to install anything? No. The tool works on any modern phone or computer browser.
How accurate are the results? The maths follows the standard formulas shown above. Real-world results vary with terrain, equipment, and conditions, so use the figures for planning.
Can I use it on my phone? Yes. The tool is designed to work on a phone screen, so you can use it at the operating desk, in the field, or at a club station without a computer.
Who uses this tool
Radio amateurs, students, and club members all use tools like this one, because they turn a formula from a book into an answer for your own station in seconds. Beginners use it to check homework and first setups, while experienced operators use it to sanity-check a plan before spending money on cable, masts, or antennas. Even a quick check can prevent a costly mistake, such as ordering the wrong cable length or aiming a beam in the wrong direction.
What to try next
- Run the tool with your real station values, not just the default numbers, so the answer means something for your setup.
- Change one input at a time and watch how the result moves, because that shows you which input matters most.
- Write the result in your station notebook next to the date, so you can compare later changes against a known baseline.
Safety note: this is an educational estimator only. Real transmissions need an amateur licence and must follow your local regulations, band plans, and power limits. Never transmit without the proper licence, and treat every result here as a planning guide, not professional or legal advice.
Versión en español: Calculadora de Altura de Antena en Longitudes de Onda – Altura sobre el Suelo en Longitudes de Onda