Model monopole radiation with practical engineering controls today. Check losses gain and mismatch instantly online. Turn antenna inputs into clear radiated power insights quickly.
The calculator uses several linked antenna power relations.
Short monopole radiation resistance: Rr = 40π²(h / λ)².
Quarter-wave reference: Rr ≈ 36.5 Ω over ideal ground.
Current method: Prad = Irms² × Rr.
Feed method: Γ = (VSWR - 1) / (VSWR + 1).
Accepted power: Pacc = Pfwd × (1 - |Γ|²).
Radiated power: Prad = Pacc × matching efficiency × antenna efficiency.
Field method: Prad = E²d² / (30G).
Here h is radiator height. The value λ is wavelength. The value G is linear gain. Loss resistance lowers efficiency. Matching loss lowers power before radiation.
| Case | Frequency | Length | Forward Power | VSWR | Ground Loss | Expected Use |
|---|---|---|---|---|---|---|
| HF vertical | 14.2 MHz | 5 m | 100 W | 1.5 | 5 Ω | Portable antenna estimate |
| Quarter wave | 100 MHz | 0.749 m | 50 W | 1.2 | 2 Ω | VHF ground plane check |
| Field survey | 27 MHz | 2.7 m | Field mode | Not used | 4 Ω | Estimate from measured field |
Radiated power is the portion of transmitter energy that leaves the antenna as electromagnetic waves. It is not always equal to forward power. A transmitter may deliver useful power into a feed line, yet some energy can return through mismatch. More energy can heat wires, coils, traps, soil, or the matching network. This calculator separates those parts. It helps you see the power that should become radiation.
A monopole works against a ground plane or radial system. Its electrical length strongly affects radiation resistance. A very short vertical has low radiation resistance. That makes ground and coil losses more serious. A quarter-wave monopole has a higher reference resistance near 36.5 ohms over ideal ground. Real ground often changes that value. Nearby objects can also shift feed impedance.
Loss resistance represents power that becomes heat. Ground loss is often the largest part for low vertical antennas. Conductor loss can matter when loading coils carry high current. Matching loss reduces power before the antenna radiates. Efficiency compares useful radiation against accepted power. Small resistance errors can change results greatly when radiation resistance is low.
Use feed power mode when you know transmitter power and VSWR. It is useful for station planning. Use current mode when you measure base current accurately. It is useful for loaded verticals and experimental work. Use field mode when you have a calibrated field reading in the far field. That mode estimates power from measured electric field and assumed gain.
Gain describes how radiation is directed. The ideal quarter-wave monopole has about 5.15 dBi gain over perfect ground. EIRP combines radiated power with gain. It is useful for coverage studies and compliance checks. ERP compares power with a half-wave dipole reference. The calculator reports both values for quick comparison.
Use realistic inputs. Measure VSWR at the antenna when possible. Include feed line loss separately if needed. Estimate ground loss conservatively for short antennas. Field readings should be taken far from the antenna. Avoid near-field readings for power estimates. Recheck units before comparing designs. Careful inputs produce dependable antenna radiation decisions every time.
Radiated power is energy leaving the antenna as radio waves. It excludes power lost as heat, reflected energy, and matching losses. It is the useful output for coverage and field strength estimates.
No. Forward power is power traveling toward the antenna. Reflected power, matching loss, ground loss, and conductor loss can reduce the final radiated power.
Use the short monopole model for electrically short verticals. Use quarter-wave reference near one quarter wavelength. Use custom resistance when measurement or simulation gives a better value.
Monopoles depend on a return system. Poor soil or few radials can waste significant energy. This is especially harmful when radiation resistance is small.
Enter the VSWR measured near the antenna feed point. If measured at the transmitter, feed line loss can hide antenna mismatch and distort estimates.
Use 5.15 dBi for an ideal quarter-wave monopole over perfect ground. Use measured, modeled, or manufacturer gain when available for real designs.
Yes. Use current mode with a custom radiation resistance. Add coil and conductor losses to represent loading network heating and wire loss.
Use it when you have a calibrated electric field measurement. The point should be in the far field, with a known distance and estimated antenna gain.
Yes. Height, ground quality, and radial layout affect impedance and radiation pattern. This calculator focuses on power, so pattern changes need separate modeling.
Its radiation resistance becomes very low. Loss resistance can then consume a large share of accepted power, leaving less power to radiate.
Use results as planning estimates only. Compliance work may require calibrated instruments, official rules, and professional review. Local regulations define acceptable radiated limits clearly.
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.