The PDL-II was designed when antenna design didn't fully understand quad and loop antennas.
Both the PDL-II and Maco V-Quad had both loops exactly the same external dimensions.
This used to be thought to be important.
Later it was found that the reflector loop could be physically larger around.
The loop spacing on the PDL -II is very close.
Maybe not bad in itself, but doesn't seem optimized.
I have seen a couple of sources claim that despite the driven loop looking like a full wave loop, its gamma match feed actually has it tuned or acting as a folded half wave element, with a quad loop reflector.
When these two antennas were designed, it was falsely thought that loop antennas didn't gain much by having more than two elements.
It has since been found that loop antennas gain as much from additional elements as Yagi antennas do.
Modern loop antennas use different size loops for the different elements.
The Maco Y-Quad (not the V-Quad) usually has a wider frequency range than the PDL-II and Maco gamma match might be slightly easier to tune.
I do like true quad loop antennas though.