How to make an antenna booster

Receiver, operating on ultra-short waves, have become a common phenomenon. We use a radio at home, in the country and even in the car. But when you delete from a broadcasting station signal quality deteriorates considerably. It is not always possible to establish an efficient receiving antenna, so the solution is to use an antenna amplifier. If you know how to handle a soldering iron and understand fundamental electronic circuits, you will be able to make such an amplifier with his own hands.

Instruction

1. Familiarize yourself with the concept of the antenna amplifier. It is made on a low noise transistor that provides a gain of about 20 dB. At the entrance of cascaded low pass filters with a cutoff frequency of 115... 120 MHz and high-pass filter with a cutoff frequency of 60... 65 MHz. This allows you to amplify the signals of broadcasting stations operating in the VHF range.
2. Make a list of the required parts. In addition to the transistor you will need a few resistors and capacitors, and inductors. The parameters of the elements shown in the figure to step 1.
3. Take the transistor type КТ3120А or КТ368А (the second option is less preferable). It is desirable to use the device imported capacitors with similar parameters of the domestic K10-17. Resistors types of MLT, C2-33 to the amplifier will be quite apt. Wrap coils of wire sew, using a mandrel with a diameter of 4 mm. Spool contains 3.5 coils L1 and L2 and 4.5 turns of wire.
4. If you plan to use the amplifier in a car the receiver, add in a scheme of two relays and an additional filter for food. When power is applied, both relays include an amplifier between the antenna and receiver. When power is off the receiver input is connected with the antenna. Version of the car amplifier will definitely provide the metal body.
5. Prepare for the installation of elements of the device printed circuit Board made of fiberglass, foil on both sides. Figure printed tracks may be different (depending on your chosen layout details). The second side of the Board Express metallic and connect the foil on the circuit with the common conductor of the top side. Cost for automotive embodiment of the amplifier run more elongated, so it was able to easily accommodate the power supply filter and relay.
6. Assembled amplifier turn on between the receiver input and antenna socket, wherein the compound is run as short as possible shielded cable. When installing the unit in the car, place it near the receiver in a shielded casing.
7. Check out how effectively the device amplifies the signal. If necessary, reduce the capacitance and increase the inductance of the coils (but not more than half). Keep in mind that in a city where the level of radio signals is high, the antenna amplifier should be switched off to avoid signal distortion.