Resonant Loop and Magnetic Loop Planning
Loop antennas can look similar, yet they behave differently. A resonant loop is usually close to one wavelength around. It uses the loop wire as a standing wave radiator. It often gives a useful feed resistance. It can be easier to match than a very small loop.
Magnetic Loop Behavior
A magnetic loop is much smaller. Its circumference is commonly below one tenth of a wavelength. It stores strong magnetic energy in the loop. A tuning capacitor cancels the loop inductance. The circulating current can become high. The capacitor voltage can also become high.
Comparison Method
This calculator compares both ideas from the same dimensions. It first finds the wavelength from the selected frequency. It then compares your loop circumference with that wavelength. This ratio tells whether the size is closer to a compact loop, a transition loop, or a full wave loop.
Magnetic Loop Outputs
The magnetic loop section estimates area, inductance, needed capacitance, radiation resistance, loss resistance, efficiency, Q, bandwidth, current, and capacitor voltage. These values help during early design. They also show why conductor size matters. A small loss can reduce efficiency when radiation resistance is tiny.
Resonant Loop Outputs
The resonant loop section checks the full wave target length. It estimates the loop diameter needed for resonance. It also gives a rough feed resistance and mismatch trend. The estimate is not a substitute for modeling, trimming, or measuring with an antenna analyzer.
Practical Safety
Use conservative inputs for safe planning. Include connector loss, joint loss, and capacitor loss when possible. High power can make a small loop dangerous. Keep people away from high voltage parts. Weather, mounting height, nearby metal, and ground conditions can change results.
Build and Test
For best accuracy, build slightly adjustable hardware. Measure resonance after installation. Then trim wire length or capacitor range carefully. The calculator gives a practical starting point for design, comparison, and documentation.
Good records also help. Save each run as a report. Compare wire sizes before buying materials. Check bandwidth before choosing a tuning drive. A narrow bandwidth can be normal for efficient small loops. It also means retuning is needed after frequency changes. Always confirm final performance with measured SWR, receiver noise, and on air reports.
Use low power tests first, and increase power only after checks.