Weak wireless signal strength in distant rooms or at home is a familiar problem for many users. Often, the router can't overcome obstacles like thick walls or metal reinforcement. In such situations, purchasing new equipment may be a waste of money.
The optimal solution is to create a homemade amplifier that will redirect radio waves in the desired direction. Remote WiFi antenna This project can significantly improve connection quality without extensive knowledge of electronics. All you need to complete this project is readily available materials and some free time.
In this article, we'll take a detailed look at the manufacturing process of a directional antenna, known as a Kharchenko antenna or "biquadrat." This design has proven to be one of the most effective for the 2.4 GHz band. You can boost your signal in areas where your router's standard antennas fail.
Operating principle and design selection
Before starting assembly, it's important to understand the basic physics of the process. Standard omnidirectional antennas radiate a signal evenly in all directions, resulting in rapid power attenuation over distance. A directional design focuses the energy into a narrow beam, creating gain (Gain).
The most popular design for DIY projects is Kharchenko's "double square." It's easy to make, requires no complex setup, and delivers consistent results. The main elements are a vibrator made of copper wire and a reflector that reflects the signal forward.
⚠️ Please note: The antenna only operates at the frequency for which it is designed. For WiFi, this is the 2.4 GHz band (wavelength approximately 12.5 cm). Changing its geometric dimensions will result in misalignment and loss of efficiency.
More complex options exist, such as wave channels (Yagi), but they require high precision manufacturing of the components. For home use, the "biquadrat" is the "golden mean" between complexity and results. It's easy to assemble from readily available materials.
Necessary materials and tools
To create an effective amplifier, you'll need a set of simple components. The base will be copper wire with a diameter of 2-3 mm. You can use electrical wire with the insulation removed, or purchase pure copper from a hardware store.
A CD/DVD disc or a piece of foil-clad PCB would be ideal as a reflector (back panel). You will also need a standard coaxial cable with a resistance of 50 Ohm (type RG-58 or RG-6) and an SMA connector for connection to the router.
For tools, prepare a soldering iron, pliers, a ruler, and a marker. Accuracy is critical here, so don't neglect measuring instruments. An error of a few millimeters can reduce the effectiveness of the entire system.
- 🔧 Copper wire (diameter 2–3 mm, length about 30 cm)
- 📀 Reflector (CD, foil, PCB)
- 📡 RG-58/RG-6 cable and SMA connector
- 🔌 Soldering iron, solder, flux
It's important to use a high-quality cable, as cheaper options have high signal attenuation. If the cable is too long, you'll lose all the gain from the antenna before the signal even reaches the router.
Calculation of dimensions and geometry of the vibrator
A key step is calculating the length of the square's side. For a frequency of 2400 MHz, the wavelength is approximately 124 mm. The square's side should be equal to a quarter of the wavelength, or approximately 31 mm. However, a velocity factor is often used to compensate for the influence of the wire and dielectric thickness.
The optimal square size for 2.4 GHz is considered to be in the range of 30–31 mm. The distance between the squares (at the feed point) should be 10–12 mm. This is the gap where the cable will be connected.
The wire must be bent at a precise 90-degree angle, forming two squares connected at one point. The ends of the wire must not touch at the junction (break). This is where the cable's core and braid will be soldered.
⚠️ Caution: When soldering, do not overheat the copper, as this will cause it to become brittle. Use a powerful soldering iron (at least 60W) to quickly heat the joint, preventing the solder from spreading across the cold metal.
The geometry must be as symmetrical as possible. Misaligned angles will alter the signal polarization and degrade performance. Use a template or paper drawing to check the angles during bending.
Reflector manufacturing and assembly
The reflector serves as a screen that reflects the signal in the desired direction. If you're using a CD, its recording surface should face the vibrator. The disc's metalized layer acts as an ideal reflector.
A hole must be drilled in the center of the reflector to allow the cable to pass through. The vibrator is mounted approximately 15–18 mm from the reflector surface. Plastic stands, bottle caps, or dielectric bushings can be used for mounting.
| Parameter | Value for 2.4 GHz | Admission |
|---|---|---|
| Length of the side of a square | 30.5 mm | ±1 mm |
| Distance to reflector | 17 mm | ±2 mm |
| Wire diameter | 2–3 mm | not critical |
| Gap in the center | 10 mm | ±1 mm |
The mount must be rigid to prevent the structure from shaking in the wind if installed outdoors. The vibrator must not touch the metal surface of the reflector, otherwise a short circuit will ruin the entire installation.
To seal outdoor antennas, the solder joints and cable connections must be sealed with hot glue or silicone. Moisture is the main enemy of homemade electronics; oxidation of the contacts will quickly render the antenna inoperable.
Connecting the cable and soldering
The most critical step is connecting the feeder (cable). The cable's central core is soldered to one side of the vibrator break, and the shielding braid is soldered to the other side. It's important to maintain symmetry in the connection.
The cable length should be kept to the minimum necessary. Every extra meter of cable introduces signal attenuation (approximately 0.2–0.3 dB per meter for high-quality cable). Try to keep the length no longer than 2–3 meters.
What is VSWR?
The standing wave ratio (SWR) indicates how well the antenna is matched to the cable. The ideal SWR is 1.0. If the SWR is higher than 2.0, a significant portion of the power is reflected back to the router, which can damage the transmitter.
The end of the cable has an SMA (Male) connector that screws into the router's port. If the router's antennas are non-removable, you'll have to carefully open the case and solder the cable directly to the standard antenna contacts on the board.
When soldering, be careful not to melt the insulation of the central core or cause a short circuit to the braid. Check the connection with a multimeter for short circuits before connecting to the router.
Setting up and testing the result
After assembly, the system needs to be tested. Connect the antenna to the router and point it toward the receiving device (laptop or phone). Use WiFi monitoring software, such as inSSIDer or Acrylic Wi-Fi.
Evaluate not only the signal strength (RSSI) but also the noise level. A good antenna should improve the signal-to-noise ratio (SNR). If the signal has increased, but so has the interference, the antenna may be picking up signals from neighboring networks.
☑️ Performance check
Experiment with the antenna tilt and rotation angle. Directional antennas are sensitive to orientation. Sometimes, just a 10-degree tilt can provide a gain of several decibels.
If there's no result, check the soldering quality and cable integrity. Often, the problem lies in poor contact in the connector or a broken core within the insulation.
FAQ: Frequently Asked Questions
Can this antenna be used for 5GHz?
No, the dimensions are designed strictly for 2.4 GHz. For the 5 GHz band, the wavelength is shorter, so all dimensions (square side, distance to reflector) need to be reduced by approximately half. The design will be significantly smaller.
Will an antenna increase internet speed?
The antenna itself doesn't increase the speed provided by your ISP. However, it improves signal quality, which allows the router to switch to a faster modulation standard (for example, from 802.11g to 802.11n), thereby increasing the actual data transfer rate.
Is this dangerous to health?
The radiated power of household routers is negligible (usually up to 100 mW) and is safe for humans, even when using amplifiers. The antenna only redistributes energy in space, but does not generate new energy.
Why does the signal appear and then disappear?
This could be due to wave interference or overheating of the router. Also, check the cable's tightness—if it's loose in the connector, it could be losing contact. Make sure the antenna is securely fastened.