The antenna is in a different environment (height, surrounding buildings, subsoil) behaves differently, sometimes the changes are very significant. The variant with a balun like FD-4 is proven. Not every band will be ideal, but even the worst case will be decent.
See: http://www.radio-foto.net/radio/windom.php
The balun must be made well – on a suitable material, suitable wire and the whole well secured against the ingress of moisture.
Suitable antennas are offered by Jirka http://www.ok5im.com/