Loop Antenna Calculator
Calculate small loop antenna radiation resistance, loss resistance, gain, Q factor, and operating bandwidth for HF and VHF applications
Formula
R_rad = 31171·(A/λ²)²
How It Works
A loop antenna is a type of radio antenna consisting of one or more wire turns forming a closed geometric shape, typically circular or rectangular. It operates by converting electromagnetic energy into electrical signals through magnetic field induction. The antenna's performance depends on its circumference relative to the wavelength, with loop size and turn count directly influencing its radiation characteristics and efficiency.
Worked Example
Consider a circular loop antenna with a radius of 0.5 meters, operating at a frequency of 10 MHz. First, calculate the loop circumference (C = 2πr = 3.14 × 1 = 3.14 meters). Next, determine the wavelength (λ = c/f = 3 × 10^8 / 10 × 10^6 = 30 meters). The loop's electrical size is then λ/circumference = 30/3.14 = 9.55. By applying standard loop antenna gain formulas, the estimated gain would be approximately -10 dBi, with an estimated radiation resistance of 0.12 ohms.
Practical Tips
- ✓Choose loop material with high conductivity like copper or aluminum
- ✓Minimize resistive losses by using thick wire or tubing
- ✓Consider environment and mounting location for optimal performance
- ✓Use precision matching networks to improve impedance matching
Common Mistakes
- ✗Ignoring conductor thickness when calculating antenna performance
- ✗Neglecting ground plane effects in near-field environments
- ✗Improper impedance matching leading to signal reflection
Frequently Asked Questions
What is the primary advantage of loop antennas?
Loop antennas are excellent for low-frequency reception, have compact size, and can be less susceptible to electric field noise compared to linear antennas.
How does loop size affect antenna performance?
Loop size relative to wavelength determines directivity, gain, and radiation pattern. Larger loops generally provide better performance at lower frequencies.
Can loop antennas be used for transmission?
Yes, loop antennas can be used for both reception and transmission, though their efficiency varies based on size and frequency.
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