salian
Disciple
Wifi routers typically come with short omnidirectional antennas. Technically speaking these are called vertical sleeve dipoles and have 360-degree coverage in the shape of a medu-wada, assuming the antenna runs through the hole in the vada.
At times it might be useful to have a directional antenna instead, say to boost wifi signal strength at a desk, or perhaps to access a wifi signal across the street.
I created this parabolic reflector that can be slipped onto any router's antenna, to make it a directional antenna.
The parabola and the position of the round holder loops of this booster antenna are mathematically designed to focus a 2.4 GHz signal on the router's omnidirectional antenna.
This wifi booster antenna:
Essentially it alters the radiation pattern. The router still uses the same power and energy but that is now focussed in a narrow-ish beam.
Wifi pentesters and users of AWUS wifi adapters might find this particularly interesting, as it enables handshakes to be captured better from a distance.
How I Designed This:
The WiFi frequencies are fairly forgiving when it comes to dimensions.
This was my design process:
The Reflector
A thin layer of aluminium reflects the wifi signals on to the antenna.
Aluminium foil from the kitchen will do in a pinch, but I had better results with aluminium duct tape that is meant for air conditioning ducts.
Make sure to burnish the tape after you have stuck it on the reflective part of the antenna. This doesn't need to be terribly flat or accurate.
Painting
You can spray paint the booster antenna for cosmetic improvement, as most paint is transparent to wifi signals.
Building this yourself
If you'd like to give this a shot, I have shared the 3D files and I'm happy to answer questions.
At times it might be useful to have a directional antenna instead, say to boost wifi signal strength at a desk, or perhaps to access a wifi signal across the street.
I created this parabolic reflector that can be slipped onto any router's antenna, to make it a directional antenna.
The parabola and the position of the round holder loops of this booster antenna are mathematically designed to focus a 2.4 GHz signal on the router's omnidirectional antenna.
This wifi booster antenna:
- boosts 2.4GHz Wifi signals from the front, by focussing signal from a larger area,
- reduces the reception of 5GHz signals, and
- reduces the reception of 2.4GHz signals from the rear.
Essentially it alters the radiation pattern. The router still uses the same power and energy but that is now focussed in a narrow-ish beam.
Wifi pentesters and users of AWUS wifi adapters might find this particularly interesting, as it enables handshakes to be captured better from a distance.
How I Designed This:
The WiFi frequencies are fairly forgiving when it comes to dimensions.
This was my design process:
- A fixed frequency 'f' in the middle of the WiFi Band is chosen
The 2.4 GHz Wifi has 14 channels, going from 2.401 GHz to 2495 GHz. An antenna tuned for the middle of the 7th and 8th channel would be approximately in the middle of the entire band. That is around 2.445 GHz, which is what we will make this antenna for. You could also design a separate antenna for the 5GHz wavelength. However 2.4 GHz band travels longer distances better.
- The corresponding wavelength λ is determined.
Using f λ = c, where c is the speed of light, we can get a value for wavelength λ.
λ = 122.6 mm is my calculated value for the frequency f of 2.445 GHz.
- A parabola with focus at a quarter-wavelength (λ/4) is generated.
λ/4 = 122.6 / 4 = 30.65mm, which is the distance we want between our router's antenna and the aluminium foil at the midpoint of the parabola.The width of the parabola depends on the size of your build plate - the larger the better. I'm using a Phrozen Sonic Mini 4K printer, with a tiny build plate, so I printed this in pieces.
The height of the booster antenna also depends on your build volume, but mainly it depends on the length of your router's original antenna.
Various methods exist to generate parabolas, depending on the software you use. I used the Parabola Calculator 2.0 software from https://mscir.tripod.com/parabola/ which gave me a good solution for the widest parabola that could fit on my printer's build plate, yet have its focus at around λ/4. The 3D model was made in Fusion 360 which is free for hobbyists.
- The existing omnidirectional antenna is positioned along this focal line, to make it directional
We create small loops to help us hold position the router's omnidirectional antenna right in this focus line of our booster antenna.
The Reflector
A thin layer of aluminium reflects the wifi signals on to the antenna.
Aluminium foil from the kitchen will do in a pinch, but I had better results with aluminium duct tape that is meant for air conditioning ducts.
Make sure to burnish the tape after you have stuck it on the reflective part of the antenna. This doesn't need to be terribly flat or accurate.
Painting
You can spray paint the booster antenna for cosmetic improvement, as most paint is transparent to wifi signals.
Building this yourself
If you'd like to give this a shot, I have shared the 3D files and I'm happy to answer questions.
