Biquadratic antenna proposed by KPKharchenko( 1961) catch meter television channels. Of course, the size was great: the wavelength was not small in size. When an antenna is required for a modem assembled from hand-made means, the structure can often be accommodated in a round box from under the laser discs, the reflector in this case is simply installed. Enough of one blank, the main thing is to look at the light so that it is not transparent( a layer of metal is required to construct the reflector).This means: the coating fits, perfectly reflects the waves of digital communication. We are talking about antennas for a modem - it implies two WiFi standards, 3G.The first has mastered the frequency of household appliances, prevents microwaves, the second is the brainchild of cellular communication. The wavelengths, of course, are similar.
Digital Modems
The word modem is a derivative of two others:
- Modulator.
- Demodulator.
Transmitting information packets, it is necessary to encode. Practitioners quickly discovered that if a person’s speech was aired, broadcasting would attenuate at a distance of 25 meters. Low frequency radio waves are not viable. The situation is better with the wires. It is well known: it was possible to transmit speech to kilometers by analog telephony, using the help of amplifiers, the frame can be moved apart. However, in this case, the conditions are alien ideal. What happens is nonsense. Each medium( air, iron, water) is endowed with a characteristic bandwidth, with the magnitude of the loss depends on the frequency. In the atmosphere, communication windows( transmitting electromagnetic radiation) used by satellite broadcasting were detected. The WiFi band( 2.4 GHz) does not apply; on the contrary, the radiation is absorbed by water vapor.
In this way, engineers gave birth to a thought: information can be transmitted by encoding a parameter of a carrier wave entering a transparency window with a useful signal. On the receiving side the information needs to be decoded. This is done by modems. Light is transmitted in lines, electromagnetic waves are encoded with useful information. Antennas are busy converting electrical oscillations into an ether wave that propagates in space. This step eliminates the need to install a communication line, wires. The broadcast will serve as the transfer of information. Convenience has to be paid for, in our case the range is severely limited, besides 99% of the energy is wasted if a pair of directional antennas aimed at each other is not used. Broadcast WiFi network, 3G inevitably leads to losses. However, the convenience of mobile communication pays off energy.
In what cases an external antenna for a modem will help:
- We see the reception on the balcony, silence is inside the apartment. The window sill signal is caught, indoors - round zero. The situation is a scourge of wireless networks for one simple reason: the power of transmitters is limited by laws. Electromagnetic waves are harmful to health, despite the desire of officials to profit, sometimes they have to give in to the elementary requirements of doctors. Not sick, others - developing laws regulating the use of hazardous substances.
- Broadcasts several towers - residents are faced with this situation: the modem, seasoned with a smart driver, stubbornly imposes a connection to a point that transmits worse. At best, it is possible to transfer manually, even it sometimes bothers. Rescue the directional antenna, which we aim in the right direction.
- In the penumbra zone, the reception of WiFi signals, 3G uncertain, is determined by the vagaries of the weather. Helps a directional antenna, aimed in the direction of broadcasting.
There are other cases. Wherever it is necessary to improve the quality of reception, you need a homemade antenna for the modem. True, one device was invented, allowing to increase the signal level. We imply a reflector. Buyers saw a 3G amplifier in the store, representing a cylindrical surface: a flash modem was installed along the axis. Rays gathered in the center, improving reception. The device is passive, the price exceeds the modem with the package for six months of the Internet. It is not surprising the question of the inhabitants of the size of a mountain, as it can be made antenna for the modem with your own hands.
Antenna Modem Designs
Let's begin with Kharchenko’s bi-quad antenna suitable for all digital communication bands. The instance catching WiFi fits in a box of laser discs, convenient in terms of weather protection. Would recommend to use online calculators, leading calculations. Since it is rather difficult to find, they took the trouble to calculate the parameters for some cases, then readers will generalize to any frequency, because the ratios will become obvious. WiFi frequencies:
- The frequency is 2.6 GHz, the wavelength is 115.3 mm. The side of the square will be a quarter wavelength: 28.82.To obtain the total length of the eight, multiply one side by 8, it turns out 230.6 mm. Take stock, it turns out 235 mm. The distance to the reflector will be 0.15 - 0.2 wavelength. We take something in between - 0.175.It turns out 20.2 mm.
In fact, a wave of 2.45 GHz is often used. We will carry out the calculation.
- 2.45 GHz frequency, the wavelength is calculated by dividing the speed of light by the number. The approximate speed of light vacuum is 3 x 108 m / s, the exact value is 299792458. We calculate the wavelength. .. we get 122.36 mm. Next, we carry out the calculation by the beaten path. We get the side of the square, dividing the wavelength by 4 - 30.6 mm. The length of the wire is calculated by multiplying by 8, it turns out 245 mm, we take the margin - 250. The distance to the reflector will be 112.36 x 0.175 = 21.413 mm.
It is difficult to bend the wire at a right angle. We recommend to use in the manufacture of the antenna for the modem vise, pliers, hammer. Along with a ruler and a corner, of course. Many have a question about how thick the wire itself should be. Let's try to answer! Reducing the frequency diameter increases, at 2600 MHz, the parameter is 2.75 mm;mastering 1300, therefore, should be taken 5.5 mm. Here are some values:
- 900 MHz - 8 mm;
- 800 MHz - 9 mm;
- 1800 MHz - 4 mm;
- 1900 MHz - 3.8 mm.
Similarly, we obtain the result for any frequency. Clearly, a violation of the thickness, the removal from the calculated values to fatal consequences will not lead, however, and too much should not be carried away. In order not to say later that the VashTechnik website contains incorrect values ... According to our information, the GSM 1800 standard is often used in the Russian Federation, let's see what kind of bi-square Kharchenko antenna should be on the operating frequency( 3G modem).
Frequency 1800 MHz, we find the wavelength: 299792458/1800000000 = 166.6 mm. Find the side of the square by dividing by 4, it turns out 41.6 mm. The total length of the wire will be 333.1 mm. With a margin of 335 mm. The distance to the reflector is 166.6 x 0.175 = 29.15 mm. Wire thickness is indicated above. Design for health.
We’ll wait for other wavelengths, the calculation procedure is obvious. We give a couple of comments on the design of a homemade antenna for a modem. If the biquadrate alone( and more we meet) reminds the eight - no more. There is no intersection at the central point. Just the wire comes closer without touching, then runs back to the sides. It reminds, indeed, the figure-eight positioned on the side( WiFi polarization is vertical).For another polarization - horizontal - we place the eight vertically.
The wire for the antenna is better to take isolated. A cable core of the desired thickness will be suitable. The material does not have to be copper, just the Olympic metal is not subject to electrochemical corrosion( always an acceptor).Protect the building is necessary in any case. As mentioned above, WiFi models are placed in a box of laser discs, which we seal for loyalty.
Eight stands on insulated racks that can be placed anywhere, but it is easier to use two supports in the area of proximity( middle).One edge is connected to the screens of the cable and antenna, the second serves to remove the signal. Both terminals are close to each other, almost in contact, there is no electrical contact at the intersection.
Signal gain will increase if you use two biquadrats. The central part is performed in this way, then the eights intersect( !) Crosswise, but at the point of contact two wires are reliably isolated from each other. The directivity pattern is narrowed, increasing gain. Good methods of catching the tower, which can be seen on the horizon. You will be able to direct the modem antenna accurately — reception will certainly improve.
The device is connected with a standard 50-ohm cable. Ideally, it is not bad to measure the CWS, then bring it to a value less than 2. The antenna device for the modem may be different, resulted in a recent review of designs resembling those used by cell phones. Radiant pads combined by matching lines.
Finishing the review, we emphasize: standards of cellular communication, WiFi remind each other. In both cases, the polarization is vertical. Made for good reception at any point. When a wave propagates around the planet, the configuration is preserved. Vertical polarization perpendicular to the ground. When talking on the radio, try to keep the antenna.
Practice! It is known for certain that blunt individuals tend to perform the simplest procedures incorrectly. Acting on display, they keep their radios horizontally, turning it in an inconceivable way. Stick to proven solutions. Sometimes it's easier to take a couple of steps. The beam rarely changes polarization, otherwise the broadcasting industry would have long taken into account the nuance( for example, a car radio, for example).
