Antenna matching device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Antennas. Measurements, adjustment, coordination

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Optimum matching of the transceiver with the antenna-feeder path is achieved by using antenna matching devices (ACS) at the radio station. They allow you to successfully operate, in particular, modern transistor transceivers that do not allow operation with an SWR of more than two. One of the problems that a radio amateur faces in the manufacture of automated control systems is the need to have a coil with a variable inductance. Such coils today are a rarity, and they are very expensive.

An obvious solution to the problem can be an automated control system with a coil, the inductance of which is changed in steps using a switch. However, using one coil with taps and a switch, it is practically impossible to ensure smooth adjustment of the inductance with a given step over the entire range of its required changes (for example, from fractions to tens of microhenries in steps of 0,1 μH).

WD8OYG described a variant of ACS (DL Kinkaid. An automatic antenna tuner. - QST, 1996, January, p. 35-37), in which nine separate coils were used. Their serial connection in various combinations allows to obtain an inductance overlap from 0,08 to 40 μH in steps of 0,08 μH for the ratings chosen by him. It should be noted right away that an automated control system with such a "variable" coil can be easily controlled only thanks to the use of a microcontroller in it, which, by making the appropriate switching, provides a consistent change in the inductance with the required step.

A simplified version of the ACS proposed by WD8OYG was developed by DL1DA (Kurt C. Schips. Kompaktes Antennenanpassgerat. - СQ DL, 1997, No. 3, s. 206, 207). It contains only ten switches. The justification for this simplification may be that a radio amateur in a stationary environment uses well-defined antennas. Having fiddled with their matching once, you can write down the obtained optimal values ​​\uXNUMXb\uXNUMXbof L and C of the matching device and set them according to the table when changing antennas and ranges. This is hardly suitable for participation in competitions, but in normal daily work it is quite acceptable.

The diagram of the ACS DL1DA is shown in the figure. It is an L- or L-shaped circuit formed by an inductor (L1-L9) and a variable capacitor C1. With switch S10, you can select the option of connecting capacitor C1 (to the input or to the output), which expands the range of resistances that can be matched by the automatic control system.

The inductance of the coils L1-L9 forms a series with a multiplicity of inductance changes close to two: 0,08; 0,16; 0,31; 0,62; 1,25; 2,5; 5 ; 10 and 20 µH. Thus, if only coil L1 is turned on (more precisely, not closed by the corresponding switch), the inductance will be 0,08 μH. If only L2 is enabled, the inductance is 0,16 uH; if only L1 and L2 are on, the inductance is 0,24 uH; if only L3 is enabled, the inductance is 0,31uH, etc.

The matcher was made for use with a QRP radio with an output power of about 10 watts, so parts from conventional broadcast receivers were used in it. Capacitor C1 is a double bank of capacitors with a maximum capacitance of 360 pF, in which both sections are connected in parallel. Switches S1-S10 are similar to P2K type switches. The coils are wound on ring magnetic cores made of carbonyl iron. When repeating the design, it is highly desirable to use annular magnetic circuits, which can provide minimal coupling between the individual coils. As an option, we can recommend (especially for higher powers) the use of dielectric ring frames and the installation of additional screens between the coils.

This matching device ensures matching of a 50-ohm path with antennas having an input impedance of 10 ...

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