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5/8 lambda antenna, GP, Hertz's half-wave dipole, radiation pattern, static, lightning protection, monopole, quarter-wave, pin, 1/4 lambda, 50-ohm cable, braid, center core, balances, half-wave pin, 1/2 lambda, KU, gain, reactance, resistance transformer, galvanic isolation, grounding, counter current, capacitance, lengthening inductance, matching, resonance, narrowband, telescopic antenna,
Greetings friends. With you again Timur Garanin.
Several times I was asked to make a video about 5/8 lambda antennas, and today finally I will cover this topic. But before moving on to 5/8 lambda antennas, you first need to talk about the evolution of GP antennas.
GP - means ground plane, i.e. horizontal plane. The task of GP antennas is to spread the signal in all directions horizontally, but not up and down.
Consider the sequence of development of GP antennas.
It all started with a half-wave dipole of Hertz. He knows how to spread the signal in all directions on the horizon and is always aligned with a 75 ohm cable. But he has a number of problems.
The first problem of the Hertz dipole in its radiation pattern is that it emits a signal not only in the horizontal plane, but also up and down, where we have no correspondents. Consequently, part of the radiated energy is wasted.
The second problem is that all the static from the Hertz dipole goes directly into the cable. There is no lightning protection here at all.
And the third problem is that the dipole consists of two halves. Installing a similar antenna for medium and long waves is a big problem, because each half can reach a length of several meters or more.
Therefore, they switched from a dipole to a monopoly. The most famous and simplest GP antenna is a quarter-wave pin. It’s just a quarter-wave rod or wire. The central core of the 50-ohm cable is connected to it, and the cable sheath in the simplest case is connected to the ground.
If it is not possible to connect the braid to the ground, then counterweights are used - rods slightly shorter than a quarter of the wavelength, located at a certain angle to the horizon. By adjusting this angle, you can make the radiation pattern narrower and raised above the horizon. The more counterweights, the more uniform the DN in the horizontal plane.
However, the quarter-wave pin still had problems. There is no protection against static, and the radiation pattern is still too blurry, which is why in the right direction, along the horizon, we get insufficient amplification.
Therefore, the next step in the evolution of GP antennas was half-wave pins. They really have a flatter radiation pattern, and therefore a larger horizontal gain. But there are serious nuances.
As we know, it is almost impossible to directly coordinate a half-wavelength segment with a cable. Because the cable is connected to the point of maximum potential, where the reactance of the antenna is much more active.
Therefore, to connect a half-wave dipole to the cable, a resistance transformer is used. On the one hand, this is an inconvenience, on the other hand, it gives some significant advantages.
Firstly, the cable with the antenna is galvanically isolated, the static does not get into the cable.
Secondly, because at the transformer output minimum current and maximum potential, the lower end of the output winding can be connected to a grounded mast. This solves the problem of lightning protection completely.
Thirdly, counterweights are not needed here, because all current flows inside the half-wave segment. Even if part of the current flows to the mast, this will not affect the balancing.
antenna # lambda # half-wave # dipole # diagram #statics # lightning protection # monopole # quarter-wave # pin # cable # braid # central # core # coefficient # reactive # resistance # transformer # galvanic # isolation # ground # counter flow # capacitive # lengthening # inductance #alignment #resonance # narrowband # telescopic # ether # timur # garanin # hertz # focus # balances # gain # ku # 12 # 14 # 58 #gp # 50 ohm
# TimurGaranin Antenna58Lyambda #GP PoluvolnovyyDipolGertsa # # # DiagrammaNapravlennosti Static Lightning # # # quarter wave monopole Pin # # # 14Lyambda 50omnyyKabel Braid # # # TsentralnayaZhila counterweights PoluvolnovyyShtyr # # # 12Lyambda KU KoeffitsientUsileniya # # # ReaktivnoeSoprotivlenie TransformatorSoprotivleniya GalvanicheskayaRazvyazka # # # Ground Kontrtok # EmkostnoeSoprotivlenie # Lengthening Inductance # Matching # Resonance # Narrowband # Telescopic Antenna # Ether