I'm not quite sure what's meaned with "match both antennas" in post #1.
You'll usually match antenna to a transmitter or receiver impedance to achieve maximum power transfer. Smith chart is a good tool to design the matching network. VNA is used to measure antenna and transmitter/receiver impedance and to verify the matching. The measurements are involving different problems, antenna impedance measurement can be disturbed by environment and cable effect. Receiver and transmitter are non-linear devices any possibly not suitable for VNA measurements. Other methods like load pulling may be preferred.