Let $(t_{j})_{j \in \mathbb{Z}}$ a increasing sequence of positive real numbers such that $$ t_{j + 1} - t_{j} \geq \gamma > 1, \quad j \in \mathbb{Z}. $$ Then for all $n \in \mathbb{N}$ and for all complex sequences $(c_{j})_{j = -n}^{n}$ we have $$ m \sum_{j = -n}^{n} |c_{j}|^{2} \leq \int_{-\pi}^{\pi} \left| \sum_{j = -n}^{n} \sqrt{\frac{1}{2\pi}} c_{j}e^{i t_{j} x} \right|^{2} dx, $$ where $$ m = \frac{2}{\pi}\left( 1 - \frac{1}{\gamma^{2}} \right). $$