Both loops radiate in phase. The reflector increases forward radiation and reduces rear radiation.
Antennas · F1SYH
BiQuad antenna
The BiQuad uses two square loops formed from one conductor and positioned in front of a reflector.
UHF
SHF
Directive
Operating principle
Main characteristics
Typical gain
Environ 10 à 12 dBi
Impedance
Proche de 50 Ω selon construction
Polarization
Linéaire
Difficulty
Intermédiaire
Dimensions and design
Each side is near one quarter wavelength. Element-to-reflector spacing is commonly near one eighth wavelength.
Construction and tuning
Step 1
Calculate the quarter wavelength.
Step 2
Form two identical squares.
Step 3
Build a flat reflector.
Step 4
Maintain element-to-reflector distance.
Step 5
Connect coax with minimal exposed length.
Step 6
Measure SWR and pattern.
Advantages
- Good gain from a simple structure.
- Reasonable beamwidth.
- Low-cost construction.
- Useful as a dish feed.
Limitations
- High precision required at microwave frequencies.
- Linear polarization in the basic form.
- Connector and coax are critical.
- Requires a sufficiently large reflector.
History and origin
The BiQuad became popular for UHF, Wi-Fi and microwave links because of its simple construction and useful gain.
Safety
Protect sharp reflector edges and observe RF exposure limits.