The GSM standard was invented by Europe in 1982, along with a few related to communication via radio telephones. The direction of the antennas was problematic, the transmitters were near the human head. Harm was noticed quickly, widely known: employees of enterprises involved in communications receive wage premiums. Without thinking twice, the standard committee introduced a new type of modulation that allows for lower power. At first, antennas were made retractable, and later acquired the appearance of hemp, which protruded from the apparatus. The filling was rapidly decreasing in size along with the power supply units; the direction of small-sized antennas of the gigahertz range is relatively young. The first developments concern the 50s of the last century. Do-it-yourself GSM antenna: how to do, where to install. Let's talk more.
The development of GSM standard, GSM antennas
Those who bother to look inside a mobile phone, another gadget, are powerless to see structures that resemble a familiar antenna. The thoughtful manufacturer constructs, more guided by experienced considerations, harmonious theory is deprived. It makes no sense to think that the review will reveal the company's corporate secrets. Beginning 3G, digital standards are constantly struggling to accommodate more information, using fewer resources. Mentioned harm, inside the cell phone emitter is located in the back wall, separated from the user by a screen-ground. Microstrip technology has long been known. The book of the 80s Veselova describes the third part of the concept.
The efficiency of a GSM cell phone antenna is low, reaching 40%.Ordinary televisions sometimes go off scale beyond 90. However, people are indifferent, health is minimal. Each swamp sandpiper praises the cellular phone, hears the interlocutor perfectly well, when the connection is broken, the opponent's sound disappears. .. So, the cellular phone is bad. The directional pattern of the GSM antenna of a cell phone is one-sided - it does not shine towards the speaker - it is strongly distorted. User hand changes the alignment of forces, what to say about the obstacles! The GSM antenna is self-made to improve reception by stationary objects. Mobility is limited to the use of car repair shops.
The GSM antennas of the transmitting stations are well equipped, radiate perfectly. We hear the interlocutor( if he does not make sudden movements), the opponent will lose packages, while jogging, in transport. The phone takes on Pyaterochka, transmits much worse. Incoming packets with the voice of the opponent regularly come, outgoing give failures.
Now readers know that it’s impossible to make a GSM antenna on microscopes at home. Eminent firms are fighting, solving the problem. The assembly, the design of the functional time takes a minimum, the production is cheap. The layout of the entrails( the antenna is not easy to fit in a modest space) is much more complicated.
The following standards are used in the Russian Federation:
- GSM 900: transmission frequency 890 - 915 MHz, reception frequency 935 - 960 MHz.
- GSM 1800: transmission frequency 1710 - 1785 MHz, reception frequency 1805 - 1880 MHz.
The microstrip antenna consists of a radiator, a dielectric substrate, and a conducting screen. With increasing thickness of the emitter increases the working range, a tenth of the wavelength. The dielectric thickness is less than the specified value. We tell for a reason. In the Wi-Fi range, microstrips are combined with grids, sealed with a plastic case, equipped with a single screen, act as a team, allowing you to get a good gain, therefore, to catch a more distant signal. The towers are fixed, are in direct view. If it is fair to say the specific situation - the solution is suitable.
Here is a picture( http: //www.carookee.net/ site) of a 2.4 GHz antenna. To start working at a frequency of 1800 MHz, it is necessary to increase the size proportionally in the ratio of 4 to 3. Note that it applies to all lines, including connecting. Try first the operation of a single square to lowering the getinax board to the needs of mobile communication. The scale of the portal is wrong - see the picture, provided with dimensions, arrows are shown. Image taken from http: //www.zero13wireless.net/.Numbers are in millimeters. In proportion remove the drawing number one, define the sizes. Square pads, if distorted, correct the graphics editor, even Paint, which is included by default in Windows, will do.
For other frequencies, feel free to extrapolate the drawing for all occasions in proportion to the wavelength ratio. Divide 2,400 MHz by the standard GSM band. Above took the ratio of 2400/1800.By acting in this way, readers will select the desired GSM antenna device. Containing 4x4 squares gives a smaller gain( amplification of the GSM antenna signal), it is easier induced. The reception is blurry, it is not clear where the signal comes from, the design is in place. In the case of a distant tower, clearly visible on the horizon, 9 squares will be appropriate. Note, the feeder to the phone( of another receiving device) should not be long, the signal will attenuate on the way here, in the cable. I want to put the device on the roof. .. collect the amplifier on the microstrip, buy ready-made in the store for the desired frequency. Find out the desired number from the mobile operator. A state frequency service has been created, ask officials to talk with private traders.
Making GSM Antenna
Most readers understand how a homemade GSM antenna can be made. The craft will require a Getinax board of suitable double-sided foil size. Copper is applied from one side - it will be necessary to add constructions of a reflector made from a sheet of steel, another metal, the area exceeding the radiator. Then the copper is drawn by the future antenna circuit. Make it more carefully using a ruler and a corner. Then:
- The area under the antenna is varnished, suitable for women for nails. The composition should not get to the surface in other places, at the joints, you can paint over large islands, then remove it with a knife( to increase the processing speed).
- The boards are etched by copper sulfate. Double-sided foil - the rear is completely painted over with varnish. Otherwise, the screen will not be dissolved! Just etching does not end in a reasonable time. Copper sulfate is not enough. The second side is not needed - they tear off with a knife. To save the screen you need to paint it with varnish.
- Etching is carried out while unnecessary areas of copper are washed away, the finished GSM antenna is washed with water, dried, and the problem areas are cleaned with a knife.
- The product is placed inside an airtight plastic case, suitable for dimensions on racks that do not affect the metal part. The screen must be grounded. Try to put on a coaxial cable braid. We remind: for WiFi the wire with a wave resistance of 50 Ohms is used. How much to take for cellular communication: 50 looks appropriate because 900 MHz television is running out.
Versions of GSM antennas
Wrote a lot about antennas for WiFi, readers guessed it: the ranges are very similar. .. just take the drawings, transfer to other frequencies, the dimensions are shown for wavelength everywhere. Transpose sketches proportionally. The procedure is described above. The network is easy to find the so-called antenna Kharchenko( biquadrat), which is a pair of frames with one common point. They brought more advanced solutions, characterized by greater gain.
Readers will have a choice of what kind of portable GSM antenna will be manufactured. Kharchenko's biquadratic construction is carried out by radio amateurs from strips 10 mm wide, with a square side centered 80 mm. We did not check the dimensions, dimensions are determined by the wavelength used by the GSM standard. For 900, 1800 MHz, the difference will be two times. Carefully check the dimensions of the drawings. The frame should be proportional to a quarter wavelength. The formula is known from the physics course; it makes no sense to give four pictures that differ in fine details. It is necessary to understand: an external GSM antenna is similar in structure to WiFi, we believe that any of the section can be transferred here. The difference is limited by frequency, modulation. The first does not affect reception, the second determines the size of the GSM antenna.
When using an extension cord, try to place the amplifier closer to the mounting point. Noise wires greatly reduce the sensitivity of the device.