Over on his YouTube channel Adam 9A4QV has uploaded a short video that demonstrates his 2.4 GHz homemade helical feed designed to be used with a reflector (prime feed satellite dish) for QO-100/Es’Hail-2 satellite reception. The antenna is made from an old can, 2-turns of copper wire, and a plastic insulator to hold the turns in place. The two turns are wound in left hand circular polarization (LHCP), because when used with a satellite dish reflector it will result in right hand circular polarization (RHCP), which is the polarization QO-100 uses.
One of the most important parts of the video is when Adam shows how he matches the antenna to 50 Ohms. He notes that without matching the antenna won’t work properly, and the return loss will be about 8 dB or even less, resulting in poor performance. With matching he obtains 30 dB return loss.