External antenna for 3G modem - reasons for using the device

Every person who bought a 3G modem, earlyor is later faced with the problem of poor signal reception. At its weak level, an external antenna for a 3G modem can help. Its use significantly increases the level of the received signal. The external antenna for 3G-modem allows at times to accelerate the initial transmission of information. It is executed in the form of a flash drive. In this case, contactless adapters are used. They re-emit the signal from the modem to the external antenna and vice versa. That is, the general scheme is as follows: one external antenna is required for the 3G modem, an internal antenna and a high-quality coaxial RF cable that has a low attenuation coefficient at a frequency of 2100 MHz. All this can be purchased in a specialized store, or you can make an external device yourself.

Simple construction

An external antenna for a 3G modem with your own hands isnot at all difficult. One of the variants of such a design is offered on the Internet quite often. This is an antenna for the Kharchenko 3G modem. It is also called the "eight" for its characteristic shape. The basis for it is the Harchenko waveguide, reminiscent of the eight of two rhombuses, which the author proposed for receiving television channels in the decimeter range. However, to use it as a 3G signal receiver, some changes have to be made to the design. It will help to strengthen the signal, if it is. If the GSM signal is not at all, it is better to use another version, based on a satellite dish. The "eight" should be made of copper wire section 4mm², which can be bought in any electrical store.

From the wire, the contour of the receivingdevice. These are two diamonds with a side of 53 mm and two angles of 120 ° on the lateral tops of the rhombuses. "The Eight does not connect in the center, as its prototype is a figure, there remains an air gap of 5mm, and this is important. The ends of the circuit are closed by soldering. From an aluminum sheet 2 mm thick, you need to cut out a plate 140x140 mm, which will play the role of a reflector. In the center of the plate, a hole is drilled for a cable with a diameter of 8-10 mm. The contour is fixed 36 mm above the reflector. He should not touch him anywhere. To do this, fasteners are made of dielectric. They can be plastic. Now you need to decide how to mount the device on the wall. To do this, you can use the bracket from the satellite dish. The cable is soldered to the antenna. It is recommended to use a coaxial cable 75 Ohm. However, it was found out experimentally that when a 2100MHz wave is received, which corresponds to the HSDPA standard, a signal of such power is generated, which instantly decays at a resistance above 50 ohms. Therefore, it is proposed to use a cable with a resistance of 50 ohms. With such a cable, the conductor is completely made of copper, and it will be easy to attach with soldering. The device must be installed and secured in place. At the other end of the cable, a matching device is being implemented. This requires copper foil. Such a foil can be obtained by dismantling an old transformer, or simply buying it in a specialized store. A special cover is made of foil. One side of this cover should be 45 mm. The case should not sit tightly on the case of our 3G device.

A cable braid will require a piece of foilthe size of 27x76 mm. The braid is soldered to this piece of foil that covers the cover, but nowhere touches it, and the cable core is soldered to the cover itself. But it also should not directly touch the case of the modem. Actually, the external antenna for the 3gG-modem is ready for operation. Now you just need to adjust it, just turning on the mount in search of better signal reception.

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