>The SteppIR 3L Yagi has a 16 ft boom.
>This corresponds to 0.46 WL on 10M,
> 0.34 WL on 15M,
> 0.23 WL on 20M.
>The W2PV Yagi Design Book shows
>gain and F/B curves for 3L Yagi's with
>boom lengths from 0.1 to 1.0+? WL
>and parasitic element tunings offset
>by 2,3,4,5,6,7 percent.
>Bottom Line: Boom lengths around 0.25 WL
>(and odd multiples) exhibit HIGH F/B ratios
>but lower gain (-1 dB), Boom Lengths around
>0.5 WL exhibit LOW F/B ratios and high gain,
>and boom lengths around 0.35 WL are a good
>compromise between gain and F/B.
>The SteppIR can be optimized for each band
>given it's FIXED boomlength, but remember that
>for full optimization ALL parameters (including
>Boomlength) must be varied. This is NOT the
>case with the SteppIR antenna. On 20M, it's
>F/B can be made to be near optimum. On 15M,
>it can achieve good gain and intermediate F/B,
>on 10M it can achieve good gain but LOW F/B
>as originally stated.
One advantage the SteppIR claims is that it
can be optimized for a single frequency without
having to worry about SWR/gain/FB bandwidth.
However, I just played around for a minutes in
YO and it appears that for a 16' boom and the
DE somewhere in the middle, 16 or 17 DB F/B is
about all you can achieve on 10 meters. Still,
it's decent F/B for most applications.
Question for a SteppIR owner: where exactly is
the DE placed on the boom?