This tunable magnetic loop antenna disassembles into small but rugged pieces and can be tuned from 14 MHz to 30 MHz.
http://dt.prohosting.com/hacks/antenna/magloop.html
The magnetic loop antenna is a high-Q tuned antenna with a very narrow pass band…typical range is 10-25 KHz. The performance of the magnetic-loop antenna is similar to a ˝ wave dipole.
http://www.elecraft.com/TechNotes/loop_ant/wd8puoloop.pdf
Different construction with good technical details about loop capacitor and its design.
http://www.qsl.net/mnqrp/Loop/Mag_Loops.htm
Design of transmitting loops up to UHF range. Has good pictures.
http://www.aa5tb.com/loop.html
It is basically a variant of the usual magnetic loop, using a toroid balun to get a reasonable match on the three bands.
http://www.g3ycc.karoo.net/rock.htm
This small styrofoam loop is a solid performer, even helping the GE SR-3 to receive more stations. It is about 14 by 11 1/2 inches. This article describes construction of a 34 by 29 inch loop.
http://www.mindspring.com/~loop_antenna/styrofoam.htm
A loop antenna for AM reception that can be folded when not in use, just perfect for portable use. When deployed, it acts exactly like a full blown loop.
http://www.mindspring.com/~loop_antenna/foldloop.htm
The antenna works properly with 50 watt rf without sparks at the tuning capacitor. Distances up to 10000 km (several times) were no problem and reports varied from 559 to 599.
http://www.iri.tudelft.nl/~geurink/magnloop.htm