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How to build a 2.4 GHz can antenna

WiFi Signal Amplifier

Is Wi-Fi bad in your apartment?

Only a soldering iron and a coffee can

The author of this antenna managed to connect to the free Wi-Fi of the hotel, located more than 400 meters from the house

Усилитель сигнала WiFi

How to build a 2.4 GHz can antenna

Suitable for wireless networks (wireless) standard 802.11b and, probably, for other applications running at this frequency.

Как построить баночную антенну на 2,4 GHz

What do you need:

1) tin can

2) N-socket ("mother") and a pair of cogs

3) A piece of 2mm copper wire

TIN

Как построить баночную антенну на 2,4 GHz

Firstly, you will need a canning, from under the paint, coffee, etc. bank. Naturally empty and clean inside. The diameter of the can should be between 7.5 cm - 10 cm, according to estimates, the most optimal size is about 9.2 - 9.3 cm (cans with half of this diameter were used successfully, I have not tried it myself). The height of the can should be more than 13.5 cm, but both lower and, of course, higher can antennas can give good results.

The jar, or at least the bottom of the jar, should be made of even tin, not wavy. I also tried a wavy, optimally short jar , the result was just as good and even better than with a can of absolutely even tin. So you can freely experiment with various banks.

However, it makes no sense to cut off the top edge of the jar, as I did . Of course, you will get more or less even edges, but without the bearing part of the bank it will easily fall apart at the seam.

N socket

Как построить баночную антенну на 2,4 GHz

I purchased an N-socket in Tevalo, however, they can be found in other similar stores. N-sockets are mainly of two types: fixed with screws and those on which there is a mounting nut. It makes no difference which of the sockets to take, I bought an option with screws (it cost about 40 crowns). If the cable coming out of your wireless network card has a different contact at the end, then you will need the corresponding socket.

Copper wire

The diameter of the wire should be about 2 mm, the length is about 3.1 cm. I got such a length from the cable remaining after electrical work, removing the insulation from it. Some sources advise using a 4 mm wire. I have not tried it myself, so I can’t advise.

Building

Cut a straight piece of about 3.1 cm long from the copper wire and solder it to the central pin of the N-socket, holding the wire as straight as possible. Be careful not to accidentally close the central contact with the side. The waveguide, or it is a piece of wire, after fixing it on the inner surface of the can, should be 3.07 = ~ 3.1 cm above this surface. You will get the exact length by fixing the nest to the bank and measuring it. The more accurate the dimensions, the better the result and the stronger the signal.

Enter your data and count

Can Diameter (cm)
Antenna Operating Frequency (MHZ)




Cutoff frequency mhz
Wavelength in the bank, Lg (cm) cm
The distance from the waveguide to the bottom (1/4 wavelength in the bank) cm
Optimal jar length (3/4 wavelength in a jar) cm
Как построить баночную антенну на 2,4 GHz

Now calculate the appropriate distance from the waveguide (piece of wire) to the bottom of the can by the diameter of your can. Good for this distance? wavelength of the conductor (guide wavelength). This distance means the distance from the inner wall of the can, and not from where the wall of the can ends. It is also necessary to precisely drill the hole, as the correctness of the distance determines how the waves will interfere and, accordingly, how the signal will amplify or weaken. The more accurate the dimensions, the better the result and the stronger the signal. The waves are reflected from the inner walls of the can and therefore, when searching for the right place, it should be borne in mind that the bottom of the can is higher than the end of the wall. Then you should drill a hole in the right place to properly secure the socket. If necessary, drill holes for mounting screws. If there is no drill at hand, you can use a nail and a file. Now it remains to fix the N-socket on the jar wall with a piece of wire soldered to it. It does not hurt to clean off the paint at the attachment point, which will improve the contact of the socket with the can. The antenna is ready, you can connect the cable and start testing.

Direction

The strength of the signal largely depends on the direction, so you need to direct the antenna fairly accurately. For example, I direct so that first I install it in the horizontal direction, and then carefully move it in the vertical direction. It is necessary to direct almost the same as the barrel of a gun, i.e. straight towards the goal. But sometimes it happens that the connection is best when the direction of the antenna does not quite coincide with the direction to the aiming point. You just have to try it.

Cap

Yeah ... to protect against radiation from inanimate and wildlife, you must close the open end of the antenna with something. For example, a suitable plastic lid that passes microwaves. Whether the lid is suitable or not can be checked in the microwave, since it works at similar frequencies. Place the test lid in the microwave oven with a glass of water (because the empty or almost empty oven cannot be turned on), turn it on for 1-2 minutes, until the water boils. And if you find that the lid has also heated up with water, then this material is not suitable in order to close the antenna hole, because he does not pass microwaves.

To remove condensation, you can make a small hole in the bottom of the antenna. This should prevent the antenna from rapidly rusting.

In general, rust weakens the signal, and cans do not resist rust for a long time. So if the connection starts to deteriorate and the direction (aiming) of the antenna, etc. no longer helps, it’s worth going to the store for a new can.

It also attenuates the signal every connection or every meter of cable connecting the antenna and network card. My approximately 10 meter cable attenuates the signal by at least a couple of decibels. So the less stuff there is, the better.

Those. characteristics

Used a Buffalo AirStation WLI-PCM-L11G card, at a frequency of 2425 MHz. Access point is located on the mast , at a distance of about 1-1.5 km. The best stable signal I received, directing exactly my jar, was this:

  • Link Quality: 13/92 (connection quality)
  • Signal level: -85 dBm (signal level)
  • Noise level: -98 dBm (noise level)

For comparison, the previous “antenna”, which was a sticking piece of wire, followed by a piece of tin, showed such maximum results:

  • Link Quality: 6/92 (connection quality)
  • Signal level: -91 dBm (signal level)
  • Noise level: -98 dBm (noise level)

Signal amplification by 3 db means an almost twofold improvement in the signal, in my case it is a fourfold difference. Link Quality at about 6-9 allows the data to move already at a speed of ~ 150-250 kb / s, so that at 13 there would already be a pretty good speed.

By the address http://www.turnpoint.net/wireless/has.htm You will find homemade antennas that show better results, but were tested at shorter distances and slightly better visibility.

Cost

My antenna cost me about 45 crowns, because I already had a piece of wire and a bank. It took about 2 hours to search for a can and build an antenna. It did not take into account the time that went into the manufacture of fasteners for cans. The cost of a new commercial antenna would probably be four-digit.

Photo

Side view

Fixed antenna 1

Fixed antenna 2

Fixed antenna 3

Bank inside

Can outside

Photo of the first antenna or what happens when you mindlessly cut the top edge of the can :)

The jar with the best signal (canned pineapples d = 9.9 cm. L = 11.5 cm) - but with a wavy bottom and walls and shorter than ideally - did not go into business because it made a hole in several places during the tests.

Mast - at a distance of 1-1.5 km.

Additional Information

(c) Asko Tamm 2002