Possibly something of interest for SOTA use is the feature article in the latest (December 2017) “Funk Telegram” magazine. This is a design by DJ4WD with full details for self construction in the 4 page article. The design is interesting in that it uses a loading coil for operation on 40m and hence keeps the overall length more manageable at under 12m. The “EGA 40” antenna can be used on 40, 20, 17, 12 & 10m without an ATU. There’s also an 80/40m version.
The author also manufactures and sells the EGA40 antenna (€ 85 plus shipping) and details are on his website at http://www.dj4wd.de/ega40_en.html.