This paper presents and evaluates a flexible rectangular loop sensor antenna designed for ice and frost detection. The study focuses on assessing the antenna's sensitivity and data transmission capabilities. The antenna features a simple loop structure that is however sufficiently sensitive to differentiate between ice and frost. This sensitivity is attributed to the internal loop, which enhances coupling with the material under test and fine-tunes the antenna's response. The antenna achieved an average radiation efficiency of 97.1 % and a gain of 2.74 dBi across the tested scenarios involving frost and ice. Additionally, it maintained a consistent direction of maximum radiation, even when loaded with ice or frost, thereby reducing constraints on the receiving antenna's radiation pattern requirements.