2.4 GHz Discone (Disk-Cone) Antenna

grabcad

This is a model of a 2.4 GHz Discone (Disc-Cone) Antenna that can be used for Bluetooth or WiFi or even FPV drones. https://en.wikipedia.org/wiki/Discone_antennaThe form is designed around LMR-200 low loss coax that has a diameter of ~ 5mm and a ~ 1mm center core. Other smaller coax types can be used.The disc is about 70% (0.7x) the 1/4 wavelength of the center frequency desired. A PCB may be used as long as the copper is thicker than the skin depth at the frequency of interest. Using solid copper sheeting is simpler, but at an increased cost.Notice that there is a flat circular diameter on the top of the counterpoise cone form. This will form a disk capacitance with the disc itself and is part of the tuning capacitance. To reduce this capacitance, extend the distance between the disc and the cone which will raise the frequency. Some trial and experimenting is necessary for best results. Cone top is ~ 2.2 mm radius -- 0.74 mm opening radius = 15.21 -1.72 = ~ 13.5 sq mmCapacitance as shown with a 2.4 mm separation = ~ 0.05 pFA 1.0 mm gap will be ~ 0.12 pF of capacitanceNote that this doesn't include other stray capacitance effects, so tuning at the bench with a spectrum analyzer is best.