When you think of directional ham radio antennas, you probably think of a Yagi, cubical quad, or a log-periodic antenna. These antennas usually are in a horizontal configuration up on a high tower. However, it is possible to build beams with a vertical orientation and, for some lower frequencies, it is far more practical than mounting the elements on a boom. [DXCommander] shows us his 40 meter two-element vertical antenna build in the video below.
A typical Yagi is just a dipole with some slightly longer or shorter elements to direct or reflect the signal. A normal vertical, however, is nothing more than half of a dipole that uses the ground as the other half. So it is possible to create reflectors and directors with a vertical-driven element.
The exact lengths and the spacing are critical and may require a bit of experimentation. [Callum] has another video (below the first one) that explains the design and math behind it. We’ve also seen arrays that require multiple elements driven out of phase to get similar effects. Of course, that requires exact lengths of cables and, in general, more cable, too.
The idea is a lot like a traditional Yagi. At higher frequencies, those can be quite portable.
This is why cell towers in the vicinity of MW (AM) transmitter sites will have an extra set of wires suspended alongside the tower. These are connected to a variable inductor/capacitor and used to “tune” the tower until it disappears at the frequency of interest. Without this tuning, the tower would act as a parasitic element and alter the carefully-engineered pattern of the transmitter just down the road.
Log-Periodic antennas made from wire are a thing. I’ve seen one at an old US Navy “remote” radio station. Example: https://www.antenna.it/military/wire.log.periodic.antenna.htm – covers 1.8 to 30 MHz with no tuner. :-)
Our now century old AM has directional power at night and is 3 towers but I seem to remember it as 6 towers years ago. We have a LPFM replacement since ’07 but with different ranges of course. HD killed it’s sound and I see “radio ranch” subdivision in it’s future. Tho other 2 AM daytimers are surrounded by subdivisions on all sides. The big tower array of 1070 WIBC on the way to Indy long a landmark has been turned into apartments.
How is a pair of phased verticals a hack when there are thousands of them out there and have been for many decades?
Umm, slow news day? This is surely just a press release for a distinctly mundane product surely?
Gain is something we hams are always looking for. With 3 you can get gain in 6 directions just by switching in and out coax to change the phase.
He does sell very nice kits, with lots of extra wire. I own two.
Fun hands-on experiment :)