5. Working band

Long-wave antennas, medium-wave antennas

　　Long wave antenna,Medium wave antenna

It is a collective term for transmitting antennas or receiving antennas operating in the long-wave and medium-wave bands. Long and medium waves propagate by earth and sky waves, which are continuously reflected between the ionosphere and the earth. According to this propagation characteristic, long and medium-wave antennas should be able to generate vertically polarized radio waves. Among the long and medium wave antennas, the more widely used vertical type, inverted L type, T type, umbrella type vertical grounding antenna. Long and medium wave antennas should have a good ground network. There are many technical problems in long and medium wave antennas, such as small effective height, small radiation resistance, low efficiency, narrow pass band, and small directivity coefficient. In order to solve these problems, antenna structures are often very complex and very large.

Short wave antenna

Transmitting or receiving antennas operating in the shortwave band, collectively referred to as shortwave antennas. Short waves are mainly propagated by sky waves reflected by the ionosphere, and are one of the important means of modern long-distance radio communication. There are many forms of shortwave antennas, among which the most widely used are symmetrical antennas, in-phase horizontal antennas, doubling antennas, angular antennas, V-shaped antennas, diamond-shaped antennas, fishbone antennas, etc. Compared with long-wave antennas, short-wave antennas have large effective height, large radiation resistance, high efficiency, good directivity, high gain and frequency bandwidth.

Ultra-short wave antenna

Transmitting and receiving antennas operating in the ultra-short wave band are called ultrashort wave antennas. Ultrashort waves mainly propagate by space waves. There are many forms of this antenna, among which the most widely used are Yagi antenna, disc cone antenna, double cone antenna, "batwing" TV transmitting antenna, etc.

Microwave antenna

Transmitting or receiving antennas that work in meter-wave, decimeter-wave, centimeter-wave, millimeter-wave and other wavelength bands are collectively referred to as microwave antennas. Microwaves mainly rely on space wave propagation, and antennas are erected higher to increase the communication distance. In microwave antennas, the widely used parabolic antennas, horn parabolic antennas, horn antennas, lens antennas, slotted antennas, dielectric antennas, periscope antennas, etc. are widely used.

Directional antennabeam antenna

A directional antenna refers to an antenna that transmits and receives electromagnetic waves in one or several specific directions that are particularly strong, while transmitting and receiving electromagnetic waves in other directions is zero or very small. The purpose of using directional transmitting antennas is to increase the effective utilization rate of radiated power and increase confidentiality; The main purpose of adopting directional receiving antennas is to increase anti-interference capabilities.

Non-directional antenna

Antennas that evenly radiate or receive electromagnetic waves in all directions are called non-directional antennas, such as whip-shaped antennas for small communication machines.

Broad band antenna

An antenna whose directivity, impedance, and polarization characteristics remain virtually unchanged over a wide band is called a wideband antenna. Early broadband antennas include diamond antennas, V-shaped antennas, doubling antennas, disc-cone antennas, etc., and new broadband antennas have logarithmic periodic antennas.

Tuned antenna

An antenna that has a predetermined directivity only in a very narrow frequency band is called a tuned antenna or a tuned directional antenna. Typically, the directivity of a tuned antenna remains constant only in the band near 5% of its tuning frequency, while at other frequencies, the directivity changes so much that communication is disrupted. Tuned antennas are not suitable for shortwave communication with variable frequencies. Nonin-phase horizontal antennas, folding antennas, zigzag antennas, etc. are all tuned antennas.

7. Various antenna vertical antennas

　　Vertical antenna

A vertical antenna is an antenna placed perpendicular to the ground. It has two forms, symmetry and asymmetry, and the latter is widely used. Symmetrical vertical antennas are often center-fed. The asymmetrical vertical antenna feeds power between the bottom end of the antenna and the ground, and its maximum radiation direction is concentrated in the ground direction when the height is less than 1/2 wavelength, so it is suitable for broadcasting. Asymmetrical vertical antennas are also known as vertical ground antennas.

　　CB 11m Ham 10m Vertical HF Antenna VERTICAL GROUND PLANE ANTENNA

Inverted L antenna

　　Inverted L

An antenna consisting of a vertical down conductor connected to one end of a single horizontal conductor. Because its shape is like the English letter L upside down, it is called an inverted L-shaped antenna. The Γ of the Russian alphabet is exactly the reverse of the English letter L. Therefore, it is more convenient to call Γ type antenna. It is a form of vertical grounding antenna. In order to improve the efficiency of the antenna, its horizontal part can be composed of several wires arranged in the same horizontal plane, and the radiation generated by this part is negligible, and the vertical part that produces radiation. Inverted L antennas are generally used for long-wave communication. Its advantages are simple structure and easy erection; The disadvantages are large footprint and poor durability.

FRP rod supports inverted L-shaped antenna inverted L antenna bracket

T-shaped antenna

　　T-antenna

In the center of the horizontal wire, a vertical down conductor is connected, shaped like the English letter T, so it is called a T-shaped antenna. It is the most common type of antenna with vertical grounding. Its horizontal part radiates negligibly, and it is the vertical part that produces radiation. For efficiency, the horizontal section can also be composed of multiple wires. T-shaped antennas have the same characteristics as inverted L-shaped antennas. It is generally used for longwave and medium-wave communication.

T-shaped antenna

Umbrella antenna

　　Umbrella antenna

At the top of a single vertical wire, several inclined conductors are led down in all directions, so that the shape of the antenna is like an open umbrella, so it is called an umbrella antenna. It is also a form of vertical grounding antenna. Its characteristics and use are the same as inverted L-shaped and T-shaped antennas.