[TowerTalk] Modeling Tri-Band Yagi Antennas

[Tony]

All:

I've noticed that most tri-band Yagi antennas that cover 20,15 and 10 meters seem to have compromised F/B ratios on the 20-meter band. Some mid-sized antennas have peak F/B ratios of only 15db on 20M, which isn't terrible, but that figure is likely to get worse as you sweep across the band.

It must be a necessary trade-off in tri-band design since JK Antennas, Optibeam and others lean towards the same compromise, which is a shame since one would want that extra F/B performance on that band.

On average, a 20M mono-band Yagi outperforms the tri-band antenna by 10db or more, which seems pretty substantial.  I'm sure someone in the group has modeled tri-band antennas like the mid-sized JK and Optibeam, and it would be interesting to know what the criteria is for the 20M performance trad-off.

Tony -K2MO