The QM8 antenna is a very simple easy to build 8 elements Ultra Wide Spaced Yagi-Uda with 1.59 m boom length for the lower 432 MHz CW-SSB-MGM band.
It exhibits a forward gain of 11.85 dBd; i.e. 14 dB forward gain over the isotropic radiator, while the F/R is about 12.5 dB.
Elements diameter is 5 mm aluminium boom is wood. It exhibits a 50 Ohms purely resistive impedance at feed point, and it is coupled to the 50 Ohms coaxial cable by the means of the 1:1 coaxial balun.
It seems ok; the impedance bandwidth is ultra wide and flat.
QM8, dimension in millimetres:
Reflector pos. 0 length 336.0
Radiator pos. 187 length 158.5 + 158.5
D1 pos……. 337 length 307.0
D2 pos……. 520 length 299.0
D3 pos……. 787 length 293.0
D4 pos……. 1058 length 287.0
D5 pos……. 1347 length 287.0
D6 pos……. 1590 length 291.0
Bob I0QM
