Homer,
I have a couple different versions of NEC, but didn't use them for this since I've built a few of them, so I don't have any fancy stuff to send you. Something that might interest you is finding a copy of Orr's "All About Cubical Quads", which I owned years ago and lost but found used on Amazon for 7 bucks. Lots of very interesting info there, including how spacing affects feedpoint impedance.
Probably most people who build quads just build the reflectors self-resonant to the lower frequency by making them longer, but I have old reference books showing both loops of a 2 element quad being made the same size (I guess to make the physical construction easier, but it probably doesn't really make that much difference) and using an open wire shorted stub to resonate the reflector at the lower frequency.
The book I mentioned has several pages on matching the quad to coax, and covers baluns and Q sections as well as gamma matches. Most interesting to me is the 10/15/20 quad using a single coax feedline and seperate but connected gamma matches for each band. Lots of ideas there (and other places) but the 1/4 wave 75 ohm section is what I setteled on with the last one because I had used it a few times before and because it's simple.
The quad I posted a photo of was very similar to your setup-- a 30' push up pole with a Channel Master TV rotator.
I think if more people understood how well these antennas worked, how cheap they are to build, and weren't caught up in owning a certain brand name or another, there would be a lot more of them in use on 27 MHz. Single band quads are not hard to build and are still small enough at 11m that you don't need 4 people to handle them. You also don't have the pattern distortion when using a quad for vertical polarization the way a yagi has when it's flipped on its side.
Lots of advantages to a quad antenna, and as you've seen they can still work well even when they're not optimized.
No comment on the frequencies there...
Rick
