A 3-element Quad-Yagi or Cubical Quad is a high-performance directional antenna consisting of three closed loop elements (typically square-shaped): a reflector, a driven element (dipole), and a director. Unlike the classic Yagi-Uda antenna with its linear elements, the Cubical Quad's loops deliver higher gain on a shorter boom and are less susceptible to man-made electrical interference.
Key Features and Advantages
- High Gain: A 3-element Cubical Quad provides approximately 8–9 dBi of gain — equivalent to a 4- or 5-element Yagi.
- Low Noise Floor: The closed-loop design reduces the pickup of static interference caused by rain, snow, and power line noise.
- Feed Point Impedance: Depending on element spacing, the feed point impedance is typically around 50–75 ohms, which makes matching to coaxial cable straightforward. Since the antenna has a balanced feed point, a 1:1 balun is required to connect the coaxial cable — it is connected at the feed terminals (marked o–ó). The balun design will depend on the operating frequency.
The calculator computes two versions of the Cubical Quad Antenna — with a feed point impedance of 50 ohms and 75 ohms — for the VHF and UHF bands. The calculation results can be exported as NEC or MMANA models for further analysis or optimization.
Schematic representation of the antenna:
Javascript source code:
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Limitations and features of antenna calculations
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| VSWR | Impedance | Radiation pattern |
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| Gain | S11 | Front/back ratio |
Antenna calculation "3-el Quad" has been added to our app for android Cantennator. Tap on the QR code if you're here on a mobile or tablet, or scan this code on your mobile if you're viewing this page on a desktop monitor to go to Google Play to download. Don't forget to rate the app and leave a review.
Related links:
- Some Model Quads Index, L. B. Cebik, W4RNL;
- The "Quad vs. Yagi" Question, L. B. Cebik, W4RNL
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