By chance I came across another web-page sharing very useful information about the material, in particular when used for radio.
Have a look:
http://sivantoledotech.wordpress.com/2010/09/03/hello-world/
http://sivantoledotech.wordpress.com/category/radio/antennas/page/2
http://sivantoledotech.wordpress.com/2010/09/18/a-tuned-active-receiving-loop/
http://sivantoledotech.wordpress.com/2011/05/10/the-trombone-magnetic-loop-for-50mhz/
