Peter, VK3YE recently posted a video on YouTube about some oblong loop antennas for 28 MHz and 50 MHz.
What attracted my attention to it was the simplicity of the antenna and it has some notable features...
1) Ease of Construction... As you can see from the diagram on the left, the 50 MHz version is only 1-metre wide and the 28 MHz version is 1.8-metres wide.
It's not hard to imagine using a horizontal non-conductive support that wide and then effectively hanging the whole structure from something like a PVC mast or even the branch of a tree.
2) Simple 50 Ohm feed point... Most loops in the shape of squares or triangles seem to have an impedance around 100 ohms and require some sort of matching device.
This oblong loop seems to have a lower impedance and is closer to 50 ohms. As a result, it can be fed directly with 50 Ohm coaxial cable. It would however be probably worth making a few loops in the coax at the feed point to make a choke balun.
3) Cost... The antenna can be made with bits of PVC pipe and some wire. It should be very cheap to make.
If you want to get on say 50 MHz then this oblong antenna would be way better than some sort of commercial vertical covering 6m, 2m and 70cms. It should also be way better than some HF antenna like a G5RV or similar that it pressed into service. In terms of bang for buck, something like this is hard to beat. You'll need to get it up high though.
Have a look at VK3YE's video below and you'll get a better idea of what it's like.