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

 

Photo

Diagram

Italian version