Beverage Antenna System

Much has already been reported about the construction of Beverage Antenne.... But:
In this project, however, symmetrical lines were used to transmit the received signals. This avoids the supply lines themselves becoming antennas. This system is also designed for up to 4 (Beverage) antennas that can be switched in the direction (i.e. 8 directions).

 

A web server is even available to select the antenna direction via remote control.

 

The concept and its individual „blocks“ are quite clearly visible on the Block Diagram:

The necessary electrical parts can be accommodated in compact boxes and are thus well protected from wind and weather, if necessary. For the sake of clarity, the boxes have the designations BOX1 to BOX5 receive.

Twinax cables (e.g. „IBM P/N 7362211“) are used to transmit the RF signals back into the "shack". A major advantage that comes with this symmetrical cable is that annoying compensating currents and radiation can be excluded from the outset. The use of „blocking filters“ can therefore be omitted. Twinax cables usually have impedances of approximately 100R to 110R.
Some transformers are required to build a two-wire beverage antenna. Of course, these must be calculated, including the cable impedance, with consideration.

BOX1 contains the first transformer: This transformer must transform the impedance of 342 ohms against the antenna wires and ground to the impedance of 565 ohms between the antenna wires. This impedance ratio of 1.65:1 results in a winding ratio of 1.29:1.

In BOX2 there is a transformer (T2) that transforms the impedance of 565 ohms between the antenna wires to the cable impedance of 100 ohms. A second transformer (T3) transforms the impedance of 342 ohms located between the antenna wires and ground to the cable impedance of 100 ohms. The impedance ratio of T2 is 5.66:1, giving a turn ratio of 2.38:1. The impedance ratio of T3 is 3.42:1, giving a turn ratio of 1.85:1.

Furthermore, in BOX2 there is a switching between the two preferred directions of the receiving antenna, available.

In BOX3, the Twinax cables (antenna signals) coming from a maximum of 4 antennas are converted to an Ethernet cable. This BOX is usually also outside the „Shack“. Compared to a Twinax cable, an Ethernet cable is relatively thin and handy. Thus, the 4 antenna signals can be guided/brought into the „Shack“ quite easily.

BOX4 contains, primarily, the relays with which the signals from the individual antennas are selected. Another relay is used to apply the control voltage, i.e. to switch an antenna direction. With 4 control signals, one of the maximum 4 antennas can be selected. Another control signal then determines the direction of the selected antenna.

In BOX5 (conventional) is the one necessary for dialing/selecting an antenna. In the simpler case, switching is done manually. For this purpose, a tap changer with 8 positions is provided. This means that for each antenna and its direction there is a position where the generation of the 5 control signals takes place via a diode matrix.

BOX5 (alternatively,) There's also another solution for switching, namely the solution: remote control via web server. For this, I built a small LAN connecteted web server (similar to the one described in another project - STM32 & W5500). This board can even be supplied via POE and provides the necessary control signals for BOX4.