To increase range of my Lora network  I decided to try a biquad antenna.

My lora frequency being 868 MHz I used this online calculator to get the proper design: https://www.changpuak.ch/electronics/bi_quad_antenna_designer.php

Then I built a jig tp help bending the 2mm copper wire. You can find it on Thingiverse : biquad antenna

This being done we attached the antenna on the roof.

Results were impressively good. Eventhough I didn't make a metal reflector for this antenna, I got a lot more power from my "Wind Only" Weather Station located 2.5 km away from the roof.

The BiQuad antenna is a simple antenna design that offers many advantages. First is the simplicity of the design. 

The radiating element are two square with the side length equal to 1/4 midband wavelength, 83.8 mm for

868 MHz in our case. 

Polarization of the antenna is 90 degrees from the position of orientation of the biquad, i.e. horizontal biquad (as shown on the roof) has vertical polarization.

The metallic reflector reflects the electromagnetic waves back to the front of the antenna (-Z-axis), hence reducing the radiation to the back and improving the antenna gain and directivity in the forward direction. The obtained gain measures the ability of the antenna to concentrate radio frequency energy in a particular direction. It is typically measured in dB and found equal to 10.5 dB for the studied antenna design.

Note that the "z axis" is perpendicular to the biquad 

Without the metal reflector my antenna behaves more or less like a dipole antenna but with better gain and directionnality.