Rectangular Vertical Loop Antenna Calculator

Calculator Input

Frequency

MHz

Loop width

Loop height

Dimension unit

Number of turns

Wire diameter

Conductor resistivity

Ω·m

Extra loss allowance

Applied power

Formula Used

Wavelength: λ = c / f

Perimeter: P = 2 × (width + height)

Area: A = width × height

Small loop radiation resistance: Rr = 31200 × (N × A / λ²)²

Skin depth: δ = √(2ρ / ωμ)

Approximate conductor loss: Rloss = ρ × wire length / effective conductor area

Efficiency: η = Rr / (Rr + Rloss + extra loss) × 100

Tuning capacitance: C = 1 / ((2πf)² × L)

How to Use This Calculator

Enter the operating frequency in MHz. Add the rectangular loop width and height. Select the matching dimension unit.

Enter the number of turns and wire diameter. Use copper resistivity for copper wire. Adjust resistivity for other conductors.

Add extra loss for terminals, joints, loading parts, and matching hardware. Enter applied power to estimate current and reactive voltage.

Press Calculate. The result appears below the header and above the form. Use CSV or PDF buttons for saved reports.

Example Data Table

Case	Frequency	Width	Height	Turns	Wire	Expected Use
HF compact loop	14.2 MHz	2 m	3 m	1	2.05 mm	Small loop study
Lower HF loop	7.1 MHz	4 m	5 m	1	3 mm	Efficiency comparison
Multi-turn test	10.1 MHz	1.5 m	2 m	2	1.6 mm	Area ratio experiment

Rectangular Vertical Loop Antenna Design Guide

A rectangular vertical loop is a closed conductor. It stands upright and forms a magnetic loop. The shape is useful when space is limited. It also lets builders choose width and height separately. This calculator helps compare those choices before cutting wire.

Why Geometry Matters

Loop perimeter sets the main electrical length. A full wave loop often works when the total perimeter is near one wavelength. A small loop is different. It uses much less perimeter. Then area, turns, loss resistance, and tuning capacitance become more important.

Width and height both change area. Larger area raises radiation resistance for small loops. Higher radiation resistance can improve efficiency. Very thin wire can add loss. Extra joints, clips, or poor contacts can also reduce useful output.

Frequency And Wavelength

Frequency controls wavelength. As frequency rises, wavelength becomes shorter. The same loop then becomes electrically larger. The calculator shows perimeter divided by wavelength. This ratio helps show whether the loop is a small, moderate, or near full wave structure.

For small loop estimates, radiation resistance follows the square of normalized area. This makes area very valuable. Doubling dimensions can greatly change results. Still, nearby walls, soil, feed lines, and mounting height can shift real performance.

Tuning And Loss

Small transmitting loops need a tuning capacitor. The estimated inductance uses an equivalent circular loop model. The capacitor value then comes from resonance at the selected frequency. This is a planning estimate, not a replacement for measurement.

Loss resistance includes conductor skin effect. It also includes optional extra resistance. That field can represent connectors, matching parts, and imperfect metalwork. Efficiency is calculated from radiation resistance compared with total resistance.

Practical Use

Use the tool to test several dimensions. Keep notes from the example table. Compare each design by perimeter ratio, capacitor value, loss, and efficiency. A design with impressive size may still be hard to tune. A compact design may need careful construction.

Final antenna behavior depends on build quality and surroundings. Use an antenna analyzer for final adjustment. Trim carefully. Retune after moving the loop. Treat high voltage points with respect, especially at higher power. Record measured changes, because repeatable data improves later antenna choices and safer tuning.

FAQs

What is a rectangular vertical loop antenna?

It is a closed wire loop standing vertically. Its width and height form a rectangle. It may be used as a small tuned loop or as a larger loop near resonance.

Is this calculator only for small loops?

The radiation resistance formula is best for small loops. The tool also reports perimeter ratio, so you can see when the design moves toward larger loop behavior.

Why does loop area matter?

For small loops, greater area increases radiation resistance. Better radiation resistance can improve efficiency when conductor and connection losses remain low.

What does extra loss allowance mean?

It represents losses from joints, clips, tuning parts, feed hardware, and matching networks. Use a higher value when construction quality is uncertain.

Can I use aluminum wire?

Yes. Change the resistivity field to match the conductor. Aluminum has higher resistivity than copper, so conductor loss may increase.

Why is tuning capacitance shown?

A small loop often needs capacitance to resonate. The calculator estimates a capacitance from loop inductance and selected operating frequency.

Is the reactive voltage exact?

No. It is an estimate based on current and inductive reactance. Real voltage depends on tuning parts, matching, layout, and measurement conditions.

Should I still measure the finished antenna?

Yes. Nearby objects, height, soil, feed line routing, and construction details can change resonance and impedance. Final adjustment needs real measurement.