"Jerry Martes" wrote
So, I'd expect the antenna's "resonance" to be defined by its
"impedance".



Antenna resonance is defined by its element's electrical properties,
"caused" by its physical properties/dimensions.
In case of 3 el "conversion" from Inv Vee, you have to picture elements as a
tuned circuits. If they are spaced within a fractions of a wavelength, they
have mutual impedance, affecting each other. As you start adding elements,
they add capacitance to the system and lower the overall resonant frequency
and impedance. Single Dipole is around 75 ohms, 3 el. Yagi around 30 ohms.
The more elements you add, the more sensitive the design is and requires
more prunning for optimum performance. So just slapping elements to Inv Vee
dipole will not produce optimized antenna. EZNEC, 4NEC2, MMANA are an
excellent tools to demonstrate that and to optimize the design, give you
dimensions and impedance and understanding behavior of antennas, give
current distribution in elements, plots of impedance, gain and other
parameters.

--
Yuri Blanarovich, K3BU, VE3BMV