The antenna was a SotaBeams Bandspringer Midi portable longwire. The radiating wire antenna was suspended on a branch of a tree about 3.5 meters above the ground (on the following image (click on the image for a larger version), the orange insulator on the yellow antenna wire is attached to the blank rope):
The other end of the radiating wire and of the counterpoise are attached on the ground using a peg.
The Z-817 tuner worked perfectly and was able to tune the antenna on 10, 12, 15, 17, 20, 30 and 40-meter bands.
During the few days before the contact, I spent several hours listening on all the bands. From my position (near Orléans, France), I heard several stations, mainly in Portugal, Italy on 40 and 20-meter bands, the other bands were quiet. I tried several time to initiate calls (calling CQ) or to answer to other calls in vain (probably due to the low transmission power) until the very last hour (I was on holidays away from home) when I successfully replied to a call from another French station.
Thus, the result of my holidays is positive thanks to this contact!