Log-periodic antennas belong to the class of directional devices. Models, as a rule, work at short waves. Most devices are equipped with a highly conductive reflector. Some modifications are made with a panel vibrator. They have one or more amplifiers. It should also be noted that there are devices with channel transmitters.
What are the main parameters of log-periodic antennas? First of all, it is important to consider the frequency of the devices. Also, specialists are considering the directivity and gain. Input impedance also affects the parameters of the antenna.
Model calculation
The calculation of the antenna is based on the length of the rack. If we consider models with one vibrator, then the reflector is used dipole type. With a length of 20 cm, the width of the panel should be 30 cm. With an increase in the size of the rack, the panel is selected corresponding dimensions.
DIY device
A do-it-yourself log-periodic antenna folds with a simple reflector, and it is more advisable to use a vibrator with an extension cord. First of all, the mast is placed directly. Racks are fixed using a welding machine. Experts advise you to immediately install an amplifier.
Wiring should only be used with grounding. To lower the frequency, expanders of different types are used. Most models are powered by contact adapters. The upper racks must be used with a small diameter. It is also necessary to pay attention to the lower adapter, from which the wire departs. Depending on the calculation of the model, the sizes of log-periodic antennas depend.
Simple receiver model
Log-periodic antennas for simple receivers are made with masts of small height. The most common are modifications to three racks. If we consider an antenna with one adapter, then the reflector is used with a capacitor. It should also be noted that the mast is fixed on the rack. A horn in this case is very rare. Adapters at the antenna are mounted through the holders. Experts say that models with dipole adapters are considered the most popular. They can work on a short wave.
Single rack device
A single rack antenna does not stand out with high conductivity. There are devices with reverse vibrators on the market. They use a fairly wide support. In this case, the holders are installed small width. If we consider a standard log-periodic antenna, it has one reflector. Racks are mounted on a mounting stand. Often antennas are sold without holders. They have a stand made with a wide base. The highest quality devices are considered to be with reinforced adapters. Vibrators can also be installed without an adapter. Racks in this case are of small length.
Model with two racks
Log-periodic UHF antenna with two racks is made with a reflector on three channels. Experts say that models have different conductivity. When choosing a modification, one must pay attention to the support of the modification. Holders can install L-shaped. Quite often, antennas of this type are installed on the roof.
Devices are well suited for receiving a television channel. However, they are not able to work at all frequencies. In this case, much depends on the shape of the reflector. Modern modifications of log-periodic type antennas are used with output amplifiers. Only open adapters are installed under them. In this case, the vibrators are mounted in the central part of the rack. Masts vary in length. Here a lot depends on the width of the racks. The conductivity of the modification depends on the reflector. The wire from the antenna should move away from the expander.
Horizontal antennas
Horizontal antenna for TV log-periodic type stands out wide stand. Many models use a long mast, and the supports are made only of aluminum alloy. If desired, such a log-periodic type antenna can be made independently. It is well suited for a low power receiver. Experts say that the holder is placed first. Only then can the mast be installed. The next step is the reflector. If we consider store modifications, they have two vibrators.
Most models are made without emphasis. Racks are in a horizontal position. For installation of log-periodic type antennas, wide metal fasteners are used. It should also be noted that there are high-frequency modifications in which an amplifier is installed. Extenders for devices are selected only high conductivity. Quite often, devices with negative polarity are found on the market. First of all, experts note that they have no problems with short waves, and a very high gain. The dimensions of log-periodic antennas directly depend on model calculations.
Vertical modifications
Often in stores there is a vertical log-periodic antenna. The calculation of the model is based on the size of the rack. Log-periodic vertical antennas are made with reflectors of different conductivity. Most models are made on contact adapters.
Also in stores you can find devices without amplifiers. As a rule, they use short reflectors, and vibrators are installed short-wave type. The minimum allowable antenna frequency depends on many factors. In this case, the user must take into account the resistance of the reflector. Additionally, you need to know the type of expander. Most models are sold with conventional controllers.
144 MHz device
Log-periodic antennas of this type are made with long racks, and vibrators are used with supports. The standard model includes one connector. Amplifiers for these log-periodic type antennas are installed of different power. It is also important to remember that modifications differ in conductivity. Some devices are made with one rack. They have a small input impedance. As a rule, they are manufactured with an output vibrator. Holders are installed small height. If desired, such a log-periodic type antenna can be made by any person. In this case, it is important to calculate the height of the rack.
145 MHz modification
The antenna for this type of TV is done only with a dipole reflector. At the same time, vibrators are used with medium conductivity. Experts say that on the market quite often there are modifications with wire adapters. Their reflectors are mounted on racks. Side supports can be very large. Also of note is the high resistance level of these log-periodic type antennas.
If desired, the model can be assembled at home. For this, specialists use metal racks that are interconnected using a welding inverter. The vibrator is used with one output. The wire from the antenna is fixed on the expander. As a rule, it is mounted in the lower part of the mast.
Copper mast model
Log-periodic antenna for T2 with a copper mast works great at different frequencies. The standard model includes a contact adapter, which is fixed at the bottom of the rack. Vibrators for models are used only with an expander. It should also be noted that the stores have antennas with wide reflectors. Most of them can work at low frequencies. Experts say that there are reverse polarization devices. For them, expanders are used with contact reflectors. Some models are equipped with amplifiers that connect to sub.
Steel mast devices
Log-periodic antennas with a steel mast can be made independently. Experts recommend harvesting wide supports for this. Most models are highly conductive and are well suited for signal reception. Vibrators for models are used with different sensitivity. In this case, amplifiers are usually installed in the lower part of the masts. Experts say that the adapter must be fixed only through the transistor and the power supply.
It is also important to note that when assembling the model, problems with the racks may arise. If we consider store antennas, then they have a wide holder. In this case, the front supports are securely fixed directly to the mast of the device.