Stack of three Antennas Combining System. Allows any of the seven combinations for 1, 2 or 3 antennas, vertically shaping the radiation lobes and changing the radiation take-off angle to optimize the signals depending on the varying ionospheric propagation angles. 7 to 30 MHz. 3 kW. N connectors. Requires a controller fed with 12 V DC 1A.

When the antenna at the 15 m (50 ft) level is used, there is a main lobe centered around 18 degrees and a deep null at 45 degrees elevation above the horizon.

When the antenna at the 30 m (100 ft) level is used, there are two main lobes, at 10 and 32 degrees and deep nulls near 20 degrees and 45 degrees of elevation above the horizon.

When the antenna at the 45 m (150 ft) level is used, there are three main lobes at 7, 21 and 36 degrees and deep nulls at 14, 28 and 46 degrees.

This shows that one antenna at one height will not cover all the incoming angles that vary through the day depending on the ionospheric propagation conditions.

Now, let's explore the combinations of selecting two antennas in phase out of a stack of three and also when the three antennas are selected at the same time.

There are four possible combinations when using more than one antenna at the time: