Surprisingly, though ham radio operators usually have a ton of radios, antennas are even more important. You can have the most expensive radio in the world, but without a good antenna for your location that is tuned properly, you’ll have a hard time getting contacts at all. So hams are always testing, building, and fiddling with antennas.
MagLoop antennas are useful for confined spaces, indoor, or stealth installs such as in apartments.
Here are some really excellent resources for designing and building MagLoops.
80-20m MagLoop Antennas – Very in depth discussion on the different variables and principals that make for a good MagLoop.
Multi-Turn MagLoop Antenna – Comparison table of variables for a 6.5ft magnetic loop antenna for 40 meters.
3-Band Magnetic Loop Antenna Design – Short schematic design for a 20-30-40 meters Magnetic Loop antenna. Includes construction details.