The quality of the radio signal for both reception and transmission is very dependent on the antenna. Antennas are of different types. They can be directional and non-directional, they can have different polarizations. But all antennas have common elements. This is the emitting part and the reduction, that is, what it is connected to the device with. They need to be calculated.
It is necessary
- - parameters of the device to which you will connect the antenna;
- - calculator.
Instructions
Step 1
Determine the type of antenna you will be making. It can be symmetrical or in the form of a beam. The signal is sent to different types of antennas in different ways. If the antenna circuit of the receiver or transmitter is inductively coupled to the circuit, it is advisable to use a symmetrical power supply scheme using a two-wire line up to 200 to 700 Ohm. For detector receivers, input devices with a grounded grid or base, and transmitters with a P-loop at the output, a single-wire "beam" antenna is more suitable.
Step 2
The most common type of antenna is dipole. It is a wire, the length of which is equal to half the wavelength of the emitted signal, and the length of each arm is equal to a quarter of the wave, respectively. For a device operating in the VHF range, these elements are made in the form of pipes or rods.
Step 3
Calculate the wavelength. It is equal to the speed of light divided by the frequency. The speed of light is taken in meters per second, and the frequency in Hertz. Consider the amendment. The speed of light in metal is less than the speed of light in air and vacuum. Therefore, a real antenna has to be made several crusts. The length of the half-wave vibrator is actually not 0.5 wavelengths, but approximately 0.475.
Step 4
Apply the signal to the beam antenna. From one end of the wire, step back a distance of 0, 171 wavelengths. At this point, connect a single-wire line to the antenna, which should be perpendicular to the vibrator wire at a distance of 0.15 wavelengths. The single-wire line can then be bent in any direction.
Step 5
A balanced antenna is connected differently. The overall length of the vibrator remains the same. Find the middle of the wire. Mark this point. Measure a section of 0.13 wavelengths so that its endpoints are symmetrical to the middle. Solder wires to these points, which at a distance of 0.15 wavelengths from the vibrator wire are soldered to the power cable, made in the form of a two-wire line. This line connects to a radio device.
Step 6
Both types of antennas have approximately the same parameters. Select this or that type of connection based on considerations of matching with the antenna circuit of the transmitting and receiving equipment.
