Avoid using your own hands to make antennas on radios for cars for the simple reason, then the equipment is difficult to adjust. Established devices at the base contain a node that resembles a nut, which allows the driver to adjust the device to the wave used. For manual models, the situation is different. An antenna for a walkie-talkie with its own hands can be made, however, for large enterprises buying a frequency, problems will arise. The State Committee monitors the goods sold so that consumers avoid mutual interference. Railways do not intersect with shipyards. Sometimes communication is required to industrialists, everyone will begin to improve equipment, we will find a situation: subscribers will hear each other. Working at different enterprises. Ask GKRCH: they will give recommendations, perhaps it will be enough to demonstrate to the experts in action the refinement to assess the impact on neighboring communication domains.
Communication and antennas of radios
It was repeatedly said: linear, circular polarization are more common in routine, the latter mostly on satellites. No exception to the radio. Horizontal polarization was taken away by television, leaving vertical broadcasting. .. walkie-talkies. Is logical. When holding the radio, the antenna is located vertically. Visible signal reflected by the terrain, rotated at a fixed angle. Due to the effect, the blunt military man demonstrates a “violation” of the laws of physics. .. The perfect reception is conducted by a vertically standing antenna. Do not believe - do the opposite!
Read reviews about homemade antennas will be amazed, but not surprised. Again, single-ended quarter-wave vibrators made from a piece of standard coaxial cable. Polarization, frequency, why something should change. Once they said: a television antenna from a cable can be placed vertically, catching a radio, find one on the desired wavelength. ..
Native antenna of the radio. Inside the knob is a copper helix, the tip of which is attached near the top. In some radios, you can simply get to the curls, in others - the problem is unsolvable. Why spiral?
According to the course of radio propagation electrodynamics, the antenna radiates in the direction of the axis, the wave will be polarized around, according to the direction of the wave. Only if the length of the coil is close to the value of the wavelength. The context in question assumes a figure of half a meter and above, forget about proximity.
The MMANA program provides an idea of the radiation pattern. The well-wishers kindly hammered the radio antenna there( 145 MHz), avoiding changing the parameters, looked at the field( opening the application):
- In a vertical polarization, an even circle appeared in azimuth. Clearly, the human body will distort the diagram! Indeed, the coil radiates vertical polarization almost evenly. The level is - 3 dBi.
- The horizontal polarization of the shape resembles the figure eight, the level is much lower. If you keep the radio with the spiral antenna horizontally, the reception will worsen, it will not reach zero.
A semicircle is formed at the elevation angle with horizontal polarization, with a dip along the vertical axis. A useful upward signal is not emitted. Let a person with a walkie-talkie climb a tree. And both hold the instrument vertically, the reception will be due only to the horizontal component, as well as the reflected signal. Here are the antennas that use the walkie-talkie. .. It is not surprising that those who like to eat are chewed up by the desire to change the design. Therefore spirals are used.
In practice - and on the MMA file - the antenna consists of a spiral, a cap plays a significant role. The idea is clear. In real conditions, the connection must be carried out in all directions, the quarter-wave vibrator is unable to provide the specified requirements. Why a quarter. Half-wave vibrator is longer. Dimensions matter. Spirals began to twist not from a full life. Just a long antenna for a walkie-talkie is too great a luxury. Pocket pierced, hand torment hold, windy weather will vomit. We have to make sacrifices. Recall, in the vertical polarization, the radiation pattern shows a similarity to the torus, typically. Horizontal adds something like a dumbbell( rough approximation), forming the missing corners, areas of space. The reception and transmission pattern is the same.
We will design walkie-talkies, removing unusual reception properties in all directions. Energy rushes in the direction of the torus. Broadcast range will increase. If we convert both radios, we get an additional gain at the cost of losing finally receiving( transmitting) from the top to the bottom. We remind you that the radiation patterns for receiving and transmitting are the same( identical).
Increase the range of the radio station by altering the antenna
The conclusion is obvious: we want to increase the range - we saw the directional pattern of the factory antenna - we need to send power to the vertical polarization, to the torus. How to make it clear, however, one question looms on the horizon - the wave impedance of the radio antenna. Do you know the meaning? They said how to measure! If the length of the feeder power line is a multiple of half the wavelength, the antenna resistance is transmitted to the output unchanged. The effect is used to measure.
A variety of instruments are used( RF generator).Thinking about this, let's say: the local oscillator of the TV is capable of producing a similar frequency, another thing to set up. Let's talk separately. You will need a high-frequency voltmeter, which is not suitable for measurement purposes. The device is measured by the voltage of the RF generator in a suspended state, the scale is calibrated to show 100%.Assemble the circuit in series:
- antenna;
- variable resistor.
Connect the generator to the circuit, measure the voltage of the resistor. Twist the adjustment until the arrow starts to show 50%.The resistance of the variable resistor becomes equal to the characteristic impedance of the antenna. It is necessary to take non-inductive resistance( which does not have its own inductance).A homemade radio antenna should, if possible, repeat the electrical parameters of the factory. Wave resistance is taken close to the original. The measurement process is understandable to readers.
Designer selection is small: two global families. Cables impedance 50, 75 Ohms. The first is applied by communication, the second - by television. The antenna of the walkie-talkie is made from the one that is closer to the nominal value of the measured value. A quarter-wave vibrator( devoid of a spiral) has a resistance of 35 ohms. The parameters of the purchased antenna is difficult to predict. It is easier for practitioners to make two antennas for a walkie-talkie using cable of a different grade. Then each experience on the ground, assessing the nature of the changes.
Making the antenna of the radio
Let us briefly recall the process of manufacturing the antenna for the radio. Considered digital television, WiFi, 3G.The audience of VashTehnik portal knows how to make an antenna for a radio. Boldly copy techniques. First you need to know the frequency. More precisely - better. Walkie-talkies have several channels, frequencies are spelled out with a passport. Select a channel by specifying the dimensions of the antenna.
Let the frequency be 435 MHz. Find the wavelength by the school formula, dividing the speed of light by the specified value: 299792458/435000000 = 689 mm. To make a quarter-wave vibrator, you need to divide the number by 4 more, we get - 172.25.The length of the antenna for the radio will be 17 cm. Try to withstand millimeters more accurately. The screen can not be cleared. Will be the receiving surface, the band will increase. Hands itch - clean off, like peel, sheath, dielectric around the main core leave.
Old antenna is soldered, a new clamp is ready for a new one. It remains to close up in place, enjoy the connection. The antenna for the radio with their own hands made. By the way, if there is no desire to remove the screen, solder together with the core in one bundle when mounting onto a microcircuit. Expanding the range is considered superfluous - better remove the screen. The first and second options are endowed with advantages, solid cable is stronger. Better to leave as is. An antenna for the radio will last longer. Take care to stick a cute cap-tip so that the copper stops oxidizing. We say goodbye exactly until the next time.
Copy factory designs. The radio sets of enterprises break down. Adapters remain, devices are thrown away. An invaluable chance for a radio amateur to prove himself. The antenna is covered with rubber, easily peeled off. Or use the accessory of the broken product. The copying process is not directly prohibited, excluding products protected by patents. The case concerns the industrial output for the purpose of sales, obtaining a fixed profit through the implementation of these actions.
