160 meters band antennas. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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The range of 160 meters, allocated to beginner shortwaves for mastering the basics of amateur radio communications, has one major advantage over other ranges and one major drawback. The advantage is that it is easier to manufacture and debug transceiver equipment for this range than for other ranges. This is very important for a beginner shortwaver. But having made a transmitter or transceiver, he immediately encounters the main drawback of this range - difficulties in manufacturing antennas. In fairness, it must be said that all shortwaves (regardless of the category of their radio stations and experience on the air) who decide to work on the 160-meter band face this problem.

The fact is that the transmitting antenna provides a high efficiency if its dimensions are comparable to the operating wavelength. Let's face it, very few hams have the ability to hang a normal half-wave dipole on this range. Firstly, this requires a free span between houses of at least 80 m. Secondly, a coaxial cable of approximately the same length is required to power this antenna. And so on...

A possible solution to the 160 meter band antenna problem is to use a wire antenna about 40 m long, fed from one end. Such an antenna can be considered as a kind of analogue of the well-known quarter-wave pin (GP - Ground Plane).

The antenna web has a vertical or inclined section and a horizontal section (Fig. 1, a, b). The ratio between these two parts of the antenna fabric is arbitrary. In particular, the canvas may not have kinks at all and go, for example, from the window of the room where the radio station is located, directly to a tall tree or the edge of the roof of a neighboring house. The total length of segments A and B for the antenna variant according to fig. 1,a - 38 m, and according to fig. 1b - 43 m.

The first version of the antenna (Fig. 1, a) with a segment length A = 10 m has an input impedance of about 10 ohms. To match it with a 50-ohm power cable, an LC circuit is used. Capacitor C achieves antenna resonance at the operating frequency, and by selecting the position of the tap on the coil L - optimal matching of the supply feeder with the antenna. It is best to control the resonant frequency of the antenna using a heterodyne resonance indicator connected to the coil L. The matching of the feeder with the antenna is monitored using an SWR meter.

The second version of the antenna (Fig. 1, b) has a higher value of the active component of the input resistance (with a length of A = 10 m, about 50 Ohm), but it also has a reactive component. It is compensated by a variable capacitor C. The resonant frequency of this antenna is set by selecting the length of the web.

There are two factors to consider when choosing an antenna option. The second version of this antenna has a higher input impedance, and, therefore, it will be more efficient due to the lower influence of losses in the "ground". But it is also more time-consuming to set up, since it may be necessary to select the optimal length of the antenna web. However, this operation is carried out only once.

For either of these two antenna options to work effectively, you need a good ground. In most cases, it is not possible for a radio amateur to install a full-size counterweight of about 40 m in length (this would be an ideal solution). However, it is always possible to install a counterweight several meters long. It can be stretched, for example, along the wall of a building from a window to a balcony or between windows. In order for such a short counterweight to work on a range of 160 meters, an inductance coil must be connected between it and the body of the transmitter (transceiver) (Fig. 1, c). Its inductance (which, of course, depends on the length of the counterweight) is calculated using a program written for GW-BASIC

10 INPUT"A=";A

20 INPUT "D="; D

30 INPUT "F="; F

40X=LOG(2000*A/D)-1

50 Y \u73.1d (F "A / 2) ^ XNUMX-T

60Z=3.28*A

70 L \u1490d -2 / F ^ XNUMX '(X "Y / Z)

80 PRINT "L"";L

90 STOP

At startup, the program asks for the length of the counterweight A (meters), the diameter of the wire of the counterweight D (millimeters) and the operating frequency F (megahertz). The result of the calculation is the value of the coil inductance L (microhenry). Check digits for checking the correctness of the introduction of the program: if A=5 m, D=2 mm, and F=1,8 MHz, then 1=207.5963 μH. In practice, it is necessary to find such a variant of the counterweight suspension so that its length is as large as possible.

Due to the proximity of the walls to the counterweight web, the actual value of the coil inductance will most likely differ from the calculated one. That is why it is better to immediately make the coil with taps and experimentally select the point of connection of the counterweight to it. This procedure can be simplified by including a variable capacitor with a capacity of about 200 pF in series with the coil. With this capacitor, the counterweight is tuned to the operating frequency. The optimal setting of the counterweight is determined by the minimum current in the auxiliary counterweight connected to the body of the radio station, several meters long. Near the body, a simple high-frequency milliammeter is included in it (Fig. 1,d).

The primary winding of the transformer T1 of the high-frequency milliammeter is a counterweight wire passed inside the annular magnetic circuit. The secondary winding of the transformer contains ten turns of wire with a diameter of 0,3 mm. The magnetic core can have an outer diameter of 5-15 mm and an initial magnetic permeability of 20 to 1000. Diode VD1 - any high-frequency.

Having debugged the antenna and counterweight in this way, it is necessary to try to connect the fittings of the house (if it is reinforced concrete), the heating and water supply system to the transmitter housing. This can increase the efficiency of the antenna.

Literature

1. Antennas for the range of 160m.-Radio Yearbook. - M.: DOSAAF, 1983, p. 66-73.
2. A simple artificial ground antenna. - KB magazine, 1997, No. 2, p. 16,17.
3. A simple artificial ground antenna. - KB magazine, 1997, No. 3. p. 37.
4. XUSE OM! - KB magazine, 1997, No. 4. With. 47.
5. shortwave antennas. - Radio Yearbook. - M.: DOSAAF. 1985, p. 165-177.
6. Stepanov B. Antenna "shortened dipole". - Radio. 1987, no. 5, p. 19,20.

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