That is to write about antennas that amateurs of ordinary means with ordinary amounts of land could reasonably buy, build and accommodate.
Sometimes though it's worth lifting budget and space constraints to see what amateurs can install.
You might never own such a station but it's great that they exist, especially when you work them from half way around the world with your QRP and dipole.
Here's a selection of some of the biggest ham antenna installations you'll see anywhere.
* KC1XX 3 element 160m array
* 7J4AAL 5 element yagi on 80m (picture)
* IW5EDI 3.5 MHz 2 element quad
* R7AB's 12 element 14 MHz yagi
PS: Want a return to reality to read about more achievable antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.