Build a BiQuad — 2.4GHz WiFi Directional Antenna
This is a WiFi/ISM-band antenna for network connectivity, not an amateur radio antenna. It operates in the license-free 2.4GHz ISM band used by WiFi, has no connection to amateur radio bands, license privileges, or Part 97, and is included here because it's a common, ham-adjacent project for getting network connectivity out to a detached shack, garage, or shed. A BiQuad uses two small wire loops in front of a flat reflector plate — simpler to build than a waveguide-style Cantenna, with a wider beamwidth that's more forgiving to aim, at a comparable gain figure.
Two Quarter-Wave Square Loops
Each of the BiQuad's two loops is a square with each side equal to a quarter wavelength at 2.4GHz — bent from a single piece of wire so the two squares share a center point, forming a shape like two diamonds side by side (or a figure-8, depending on orientation). The antenna is fed right at that shared center point.
The Reflector Plate
A flat metal reflector plate mounted a set distance behind the loops directs the antenna's radiation forward, adding gain and front-to-back ratio the same way a reflector element works on a Yagi or a corner reflector.
BiQuad vs. Cantenna — Different Tradeoffs
- Construction: the BiQuad is simpler to build — bending wire and mounting a flat plate, with no waveguide-mode calculation or precision probe placement to get right.
- Beamwidth: the BiQuad has a noticeably wider beamwidth than a Cantenna, making it more forgiving to aim and often preferred for a wireless bridge where precise, ongoing aiming adjustment isn't practical.
- Gain: roughly comparable between the two designs for similarly-sized builds — the choice generally comes down to which is easier to build and mount for your specific situation.
What This Antenna Is For
Like the Cantenna, this is a directional point-to-point or point-to-multipoint WiFi antenna — aim it at a distant access point or another directional antenna to extend a wireless network link, for example between a house and a detached shack. It is not omnidirectional.
| Parameter | Dimension | Notes |
|---|---|---|
| Each loop side length | 30.75 mm | Quarter-wave, bent from a single wire per loop pair |
| Total wire length (both loops) | 246 mm | 8 sides total, fed at the shared center point |
| Reflector spacing behind loops | 30.75 mm | Quarter-wave, same as the loop side length |
| Suggested reflector plate size | 123-148 mm square | Roughly one free-space wavelength across |
BiQuad Dimension Calculator
Materials for a complete BiQuad build
Building the BiQuad
Most of the build is precise wire bending — take your time on the loop shape before soldering.
Cut the Wire
Cut a single length of solid copper wire equal to the total wire length from the calculator, plus a small allowance for the feedpoint connection at each end.
Bend the Two Loops
Bend the wire into two adjoining squares, each side equal to the calculated side length, meeting at a shared center point where both loops' ends come together.
Prepare the Reflector Plate
Cut the reflector plate to size and mark the feedpoint location where the loops' center point will sit in front of it.
Mount the N-Connector
Install the panel-mount N-connector through the reflector plate at the marked feedpoint location.
Mount the Loops in Front of the Reflector
Using the non-conductive standoffs, mount the completed wire loop assembly at the calculated spacing in front of the reflector plate, with the loops' shared center point aligned to the N-connector.
Connect the Pigtail Cable and Mount
Connect your N-to-radio pigtail cable, mount the assembly in a bracket or enclosure, and aim it toward the distant access point or antenna.
Verify the Link
Connect to your WiFi radio and check signal strength/link quality on both ends, adjusting aim as needed.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| No signal improvement at all | Feedpoint wiring reversed or shorted, or loops not closed properly | Check continuity and polarity at the N-connector feedpoint | Re-solder the feedpoint connections, checking each loop's wire routing |
| Weak link despite correct construction | Reflector spacing incorrect, or poor aim | Measure the actual reflector-to-loop spacing against the calculator | Adjust spacing to the calculated value; fine-tune aim |
| Loop shape uneven or distorted | Inconsistent bending during construction | Compare each side length and angle against the target dimensions | Re-bend using a jig for consistent corners |
| Connector loose or leaking after outdoor exposure | Insufficient weatherproofing | Inspect the connector mount and enclosure for water ingress | Re-seal with weatherproof sealant or add a weatherproof enclosure |
| Link works but is inconsistent | Wind moving the aimed antenna, or 2.4 GHz interference from other devices | Check mounting rigidity and scan for nearby WiFi/Bluetooth congestion | Secure the mount more rigidly; try a different WiFi channel |
Is this an amateur radio antenna?
No — this operates in the license-free 2.4GHz ISM/WiFi band, unrelated to amateur radio bands or license privileges. It's included here because getting network connectivity to a detached shack is a common, ham-adjacent project.
Is a BiQuad better than a Cantenna?
Neither is strictly better — they trade off differently. The BiQuad is simpler to build and has a wider, more forgiving beamwidth; the Cantenna can be built longer for somewhat higher gain and a narrower, more precisely-aimed beam. Choose based on your construction preference and how precisely you can aim and maintain the antenna's position.
Does the reflector plate material matter?
Any solid conductive metal sheet works — aluminum and copper are both common choices. What matters more is getting the size and spacing close to the calculated values.
How precise does the wire bending need to be?
Reasonably precise — aim for consistent side lengths and square corners using a jig, since an uneven loop shape will detune the antenna somewhat and reduce performance, similar to any resonant wire antenna.
Can I mount this indoors pointed through a window?
Yes, many builders do exactly this for a shack link — window glass causes some signal loss but not enough to prevent a workable link at typical residential distances, and it avoids weatherproofing the antenna itself.
Can I use this for a car WiFi hotspot or other non-shack use?
The design works the same regardless of application — any 2.4GHz WiFi point-to-point link can use this antenna, though this guide focuses on the shack/detached-building use case.