Variable termination using a Vactrol or some other method is an absolute must. Peak performance cannot be realized with a fixed resistor.
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay6.html
Antennas up to 150 feet in length, and maybe just a bit more, should give full medium wave coverage
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay10.html
The K9AY turns out to be an excellent performer, able to beat the Beverages in some cases.
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay24.html
Experimenting with two wires shows a greater gain. More experiements needed to fully explain why
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay19.html
The K9AY antenna doesn't work without ground. It needs really good ground to performe optimal.
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay14.html
While the K9AY is a crossed-X delta loops, other wire shapes may give good results
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay16.html
Two ways of producing your own Vactrols for use with your homemade K9AY.
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/vactrol.html
some experimentation is required determining the distance above ground of the lower part of the K9AY loop
http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay20.html