An ultrashort wave receiver has become commonplace for a long time. We use the radio at home, in the country, and even in the car. But with distance from the broadcasting station, the signal quality deteriorates noticeably. It is not always possible to install an effective receiving antenna, so the solution to the problem may be to use an antenna amplifier. If you know how to handle a soldering iron and understand electronic circuitry, you can make such an amplifier with your own hands.
Instructions
Step 1
Check out the schematic diagram of the antenna amplifier. It is made on a low-noise transistor providing a gain of about 20 dB. At the input, low-pass filters with a cut-off frequency of 115 … 120 MHz and a high-pass filter with a cut-off frequency of 60 … 65 MHz are connected in series. This allows you to amplify the signals of broadcast stations operating in the VHF range
Step 2
Make a list of the parts you need. In addition to the transistor, you will need several resistors and capacitors, as well as inductors. The parameters of the elements are shown in the figure for step 1.
Step 3
Take the transistor type KT3120A or KT368A (the second option is less preferable). It is advisable to use imported capacitors in the device, similar in parameters to domestic K10-17. Resistors of types MLT and C2-33 will be quite suitable for the amplifier. Wrap the coils from the PEV wire using a mandrel with a diameter of 4 mm. Coil L1 contains 3.5 turns and L2 contains 4.5 turns of wire.
Step 4
If you plan to use the amplifier in a car receiver, add two relays and an additional power filter to the circuit. When power is applied, both relays turn on the amplifier between the antenna and the receiver. When the power is turned off, the input of the receiver is connected to the antenna. Be sure to provide the car version of the amplifier with a metal case.
Step 5
Prepare a printed circuit board made of fiberglass foil-coated on both sides for mounting the device elements. The pattern of the printed tracks can be different (depending on the layout of the parts you choose). Leave the other side of the board metallized and connect with foil along the contour to the common conductor of the upper side. Make the board for the automotive version of the amplifier more elongated so that you can easily place the power filter and relay on it.
Step 6
Connect the assembled amplifier between the input of the receiver and the antenna socket, and make the connection as short as possible with a shielded cable. When installing the device in a car, place it near the receiver in a shielded casing.
Step 7
Check how effectively the device amplifies the signal. If necessary, reduce the capacitance of the capacitors and increase the inductance of the coils (but not more than one and a half times). Please note that in an urban environment where the signal level of radio stations is high, the antenna amplifier should be turned off to avoid signal distortion.
