Calculate monopole dimensions for faster field planning. Compare wavelength, trim margin, and practical build values. Tune vertical radiators with confidence across real installation conditions.
The page uses a clean white style with a responsive calculator grid: three columns on large screens, two on medium screens, and one on mobile.
The calculator combines free-space wavelength with construction multipliers that represent conductor velocity, end effects, and any loading used to shorten the build.
Wavelength (λ) = c / f Physical Length = λ × Element Ratio × Velocity Factor × End Effect Factor × Loading Factor Start-Long Build Length = Physical Length × (1 + Trim Margin / 100) Suggested Radial Length = λ × 0.25 × Velocity Factor × End Effect FactorThe ground planning score is a heuristic planning aid based on radial count and stated ground quality. It is not a substitute for field strength measurement or impedance analysis.
These examples use common planning values and help you sanity-check results before cutting material.
| Frequency | Type | Velocity Factor | End Effect | Loading Factor | Calculated Length |
|---|---|---|---|---|---|
| 7.1 MHz | Quarter-wave | 0.95 | 0.98 | 1.00 | 9.8277 m |
| 14.2 MHz | Quarter-wave | 0.95 | 0.98 | 1.00 | 4.9139 m |
| 27.2 MHz | 5/8-wave | 0.95 | 0.97 | 1.00 | 6.3479 m |
| 146 MHz | Quarter-wave | 0.95 | 0.97 | 1.00 | 0.4730 m |
A radiator is usually easier to shorten than lengthen. Starting slightly long gives you room for final tuning after installation, grounding, and feed line effects are present.
Velocity factor scales the physical length to reflect real construction behavior. Wire insulation, conductor geometry, and nearby structures can shift the required cut length away from a simple free-space estimate.
The radiator tip and surrounding environment introduce capacitive behavior that changes resonance. The end effect factor lets you apply a practical correction before field trimming begins.
Yes. Select the 5/8-wave option and apply realistic construction factors. Remember that many 5/8-wave verticals need an impedance matching method at the feed point.
Not directly in the core length equation. It mainly affects system performance, losses, and tuning behavior. The calculator shows a planning score to reflect that ground-system quality matters.
No. The resistance value is only shown for electrically short monopoles using a basic approximation. Practical feed-point impedance depends on height, ground losses, matching, and installation details.
Use the graph for planning and sensitivity checks. Final tuning should still be verified with measurement tools such as an antenna analyzer, VNA, or careful SWR testing.
Yes, at a planning level. Reduce the loading factor to represent physical shortening. After that, confirm the final dimensions with real measurements because loaded antennas are especially installation-sensitive.
Monopole antennas are strongly influenced by installation details. Ground conductivity, radial geometry, feed line routing, mounting height, nearby metal, weatherproofing, and final enclosure shape can all shift resonance. Use the calculated length as a strong planning baseline, then verify with measurement and trim carefully.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.