On 630 metres and 2200 metres, what key antenna characteristic must be taken into account to comply with power limitations expressed as equivalent isotropically radiated power (EIRP)?

Equivalent isotropically radiated power (EIRP) is calculated by multiplying the transmitter power supplied to the antenna by the antenna's absolute gain. Therefore, on low-frequency bands like 630 metres and 2200 metres where strict EIRP limits apply, factoring in the antenna's gain is essential to ensure regulatory compliance. Impedance, resonance, and bandwidth are important for efficient antenna tuning and operation, but they do not directly dictate the mathematical radiated power limit. Because low-frequency antennas are typically physically small relative to the wavelength, their gain is usually negative (a loss), which drastically affects the actual radiated power compared to the transmitter's output.