Searching for some horizontally polarized omnidirection 50Mhz antenna beyound the well known HALO antenna, i found this very interesting design by PE1ITR. It seems to be more omnidirectional than HALO design and a little bit more gain too.
Basicaly this is made by 2 bent dipoles fed with 90 degrees shift from each other. Stacks of 2 of it will lead around 8.5 dbd on a flat and low angle irradiation pattern.
Check this out: PE1ITR – 50MHz Omnidirectional Antenna
Irradiation pattern – Horizontal plane
The antenna itself