I did this with a Hy-Gain 105BA. The question is are you trying to optimize
on the same boom or use it to build on for a much larger antenna. At the
end of the day, you are simply buying the hardware at a convenience and
discount vs doing it fully from scratch. But the actual antenna design is a
completely new antenna.
I turned a 105BA into an 8el 10M yagi on a 40 ft boom, fixed to the tower
aimed at EU. It's a killer antenna. I built 3 additional directors and
adjusted the elements on the 105BA to match the model. Its essentially an
optimized for forward gain 8 el yagi.
The boom extender is 24 ft of 2.5 inch boom with a few feet of 2.25 inch
"coupling" down to the 2 inch supplied boom halves. A total of 40 ft end to
end with overlap for strength. It is trussed with small philly on each end
to pull up the slack.
The only mod I did to the 105BA is to further secure the DE insulated
elements vs the flimsy compression of the 105BA design. I am also using a
different balun. SWR 2:1 from 28000 - 28800. OWA is better on 2:1
bandwidth but not as good on gain.
Ed N1UR
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