These tri band quad loop antennas were popular in the seventies, as I 
recall, and one of my nephews living in North Dakota had one and loved it. 
I new two guys here in Denver who each built what they called their monster 
quads.  They were 5 element quads, I forget the boom length, but they also 
worked lighting up two full sized elements on 40 meters.  They ran big, and 
I do mean big, amps, too, but they both drank a lot, ha ha.  I had a friend 
in western Colorado who ran a 2 element full sized 40 meter quad one season 
on an 85 foot tower.  He still claims to this day he has never had a better 
40 meter antenna.  They used to say, a 2 element quad was equal to a 3 
element beam but I don't know if anybody ever proved that.
 Everyone I know who owned one, regardless of where they lived in the 
country, said they got tired of stringing new wire loops due to breakage.
Phil.
K0NX