“The first application I worked on was the design of wideband Yagi antennas (>10% 2:1 VSWR bandwidth at the design center frequency) for various amateur bands, ranging from 1.25m to 13cm. The motivation behind this was that, typically, one would need to buy two antennas from companies such as Directive Systems or Down East Microwave to cover an entire amateur band. However, if performance is comparable, it is more economical to build a wideband Yagi using materials from a local hardware store.
Ultimately, I was able to achieve ~10% bandwidths by carefully adjusting the element radius and spacing for the first three elements. I also achieved forward gain within about 1dB of a gain-optimized Yagi, with F-B ratios of 20 dB and sidelobes (the trickiest part) suppressed to around -15 dB at worst.
CENOS development team has done an excellent job up to version 4.0 beta (the latest version I have used). This is the first (relatively) serious RF design I have worked on since my time at PPPL in the late 1970s. While the learning curve has been steep, using modern tools and test equipment has made the effort worthwhile—things move much faster now.”
