There is calculator for building magnetic loop antenna. Try this calculator, to see hows the performance before making you own magnetic loop antenna. Performance may vary, but why don’t you try ?
http://dl.dropbox.com/u/8414601/amateur%20radio/loop-calculator.xls
http://dl.dropbox.com/u/8414601/amateur%20radio/aa5tb_loop_v1.22a.xls