Quite a few people who use WSPR use the tiny Microvert Antenna whose design seems to have originated in Germany. For example, this diminutive antenna is only about 30cms long on 28MHz. It uses the coax intentionally as a counterpoise with an RF choke the right distance down the coax. Performance is several S points down on a full sized antenna like a 1/2 wave dipole. With small antennas there is always a compromise! Versions have been made for most HF bands. The antenna looks ideal for portable or balcony use, being small and easy to erect. Perhaps I should test my (currently poor) build skills by making one for 10m or 20m WSPR use?
I wonder who reading this post has used a Microvert Antenna and how they found it?
See http://download.antennex.com/preview/archive4/Apr601/microvert.pdf .
This looks like an easy antenna to take on the trail. But I just had to research an opposing argument: http://cq-cq.eu/mv.htm, but I will try this later as I’m limited by overhead wires.
Have had pdf on the Microvert since living in HOA, but got by with OCF dipole in attic. Going mobile now, so looking for something small for 20 meter. Have dimensions pretty well done, just finding as much on the antenna as I can. The Antennex pdf is not reachable??!!