I am about to install a Multi-Band loop which will be resonant on 40m, 20m, 15m and 10m. It needs a 4:1 balun - but other than this balun, this is cheap to build and is well within the possibilities of many small ham radio stations. It will give me some TX *and* RX gain on the higher bands and it will also be a lovely TX / RX antenna during the day for NVIS 40m.