I'm interested in the performance of home-made loop antennas for the
AM broadcast band compared to some of the commercial units such as the
Select-a-Tenna, or the twin ferrite antenna from www.ccrane.com

How do the commercial units compare to homemade loops of somewhat
larger size?

I have constructed a loop antenna about 15 inches square using a
wooden cross frame and about 16 turns of #22 copper wire all in
parallel with a 360 pF variable cap. The results are good and the Q of
the antenna appears to around 120 or more near the low end. I can set
a portable AM radio next to the antenna and easily fine tune a weak
station to much louder volume, but I'm not sure what gain I'm getting
from the system and can't make a comparison.

I'm wondering if size of the loop (and resistance of wire) are the
only considerations to the performance of passive loop antennas, or
are there other considerations? And how would this antenna perform
compared to commercial units of smaller size?

-Bill