If you read old antenna books, you’ll probably see the idea of phased vertical antennas. These use certain lengths of coax to control the phase of a signal going to three verticals in a triangular configuration. Depending on the phasing, you can cause the array of antennas to be directional in one of three directions. [DX Commander] designed a very modern version of this antenna and shows the theory behind it in a recent video that you can see below.
It seems another ham built the antenna and a control box for it which he’s sent to [DX Commander] although he hasn’t set it up yet to create an 80 meter directional antenna. We’ll be interested in seeing how it works in practice.
Of course, the phasing delay line and the verticals will be tuned to a specific frequency, so you can’t expect this to be a broadband system. It isn’t small either since the verticals are placed a quarter wavelength apart and you need about the same amount of coax for the phasing cable (accounting for velocity factor).
The control box can select which vertical gets the delay and that controls the direction. You can also switch the delay out completely and wind up with an omnidirectional antenna.