Let me also point out that the two places where the QDFA has been tested before have much better ground than the rocky, stony morenes in Kongsfjord. Dallas Lankford mentioned that EZNEC simulation did not give any answer as to how the QDFA would perform over lossy ground. Maybe this real-world test does.
Last night we compared the QDFA with two beverages (and even one pointing way off North America). The 310 is my favourite nighttime beverage because of less European QRM than the 340. The latter performs best during daylight hours. So basically, the competition was between the QDFA and the 310. Conditions favoured the eastern part of the USA and Canada. Signal levels were from threshold to "fair".
In short, there was no significant difference. On upper MW, the signal-to-noise levels were roughly the same or a few dB in favour of the QDFA. Readability was mostly the same. What I heard on the QDFA I could also hear on the 310. The reduced sensitivity of the QDFA revealed itself on frequencies like 740 (Ontario) and 590 (Newfoundland) where the 310 had audible and even readable levels (590) and the QDFA couldn't hear any audio. On an undisturbed frequency like 1650 (Ontario) the QDFA and the 310 were identical. The QDFA was less sensitive to Loran C noise though, even if the Loran C station is in its front lobe.
So, is the QDFA a failure? Definitely no. It is probably just placed on the wrong spot, and even then it matches the 310 in performance, at least on the upper half of the MW band. It has a wide front lobe, and it can null a very wide angle off the back. And it is extremely quiet. It performed somewhere along the lines Dallas Lankford had predicted (or feared), given the lossy ground. Since it was an astounding success at Grayland, it should be equally good on a European site with good ground conditions.
The downside is of course that you have to make it yourself and it takes up quite a bit of space (120 meters from end to end). And you need to make sure that the deltas don't collapse if you're in a windy location.