Part of me is of a
mind that Wspr should be omnidirectional. However most
people on 4m use horizontal yagi antennas. There are good
reasons for this which I don't need to go into here. I did try
a turnstile (horizontal omnidirectional antenna) back in 2010.
It was unsuccessful. However there were very few stations
around and no map tab on the website to advertise my presence.
Perhaps I will return to this one
Simple turnstile tried back in 2010.
At the moment a horizontal dipole would seem to be the minimum
requirement, with a yagi the de facto default.
Currently I use a 3 element yagi.
I have one of these, a Sirio CX-4-68. It is nicely made and
appears to be a J-pole. It tunes really well too.
I am ready if ever anyone decides to go vertical - HI!