Hi Ignacio,
Thank you for showing us your solution, very interesting!
I experimented as well with such kind of antennas, also mainly for space restricted summits.
I wanted an antenna that is usable between 40m and 6m, without the need of a tuner. It should be easily and fast deployable, either by a composed earth stake, some stones or supported by the backpack.
Like Ed @DD5LP, I experimented with the well known Kommunica/Gabil/Sharman branded antenna, or in my case, with a clone from WIMO.
The whole antenna system, including a ground spike, 3m of RG-174, 8 radials and wire winder weights in total 740g and needs little space in the backpack.
I created a short video that may give you some inspiration for your own solution:
The video description contains further information about all used parts.
73 Stephan