Small Transmitting (Magnetic) Loop
Loop Antennas
A compact tuned loop, far smaller than a wavelength, with sharp tuning and high efficiency.
- Band
- HF (typically 80-10 m)
- Gain
- ~ -3 to +1 dBi (size dependent)
- Polarization
- Linear (plane of the loop)
Photos
Radiation / wave patterns
How & why it works
A small transmitting loop is a single turn of large-diameter tubing, much less than a wavelength around, resonated by a high-voltage vacuum or butterfly capacitor. Because it is electrically small, almost all the stored energy is in the magnetic near field, giving it a very high Q: tuning is razor-sharp and bandwidth is narrow, but a well-built loop can be surprisingly efficient and is far less sensitive to nearby electrical noise than a comparable short whip. Its compact size and deep nulls make it ideal where space is limited.
Real-world uses
Apartment and stealth HF stations, portable operation, and direction finding.