This article describes VK4MQ’s (Bruce) build of the antenna and documents measurement of the prototype two element Yagi for Fox Hunting / portable direction finding: Prototype 2el Yagi for 146MHz Fox Hunting . See the original article for the design criteria.
A prototype was constructed and tuned to approximately mid band.
Above, the antenna pointing at the zenith for measurement.
Be aware that small changes in element lengths and spacing may be required for optimal performance, don’t commit these until optimised.
Above are the measured |s11| and VSWR curves with the antenna pointing to the zenith.
Observations included that the Front/Back ratio was consistent with the model, the antenna was quite symmetric (it could be rolled about the boom axis and boresight followed the boom), and had deep nulls at approximately 110° from boresight.
For Foxhunting, Front/Back is useful for identifying the approximate direction of the signal, the side nulls are useful for quite precise bearing if you have calibrated that angle (ie, you know the angle from observation of a known source).