The performance of an acousto-optical tunable filter (AOTF) depends on several key parameters, such as the diffraction efficiency and the applied RF signal at the external network of the transducer. The latter has a specific bandwidth in which its efficiency is high. The goal of this paper is to experimentally investigate the relationship between the electrically matched RF bandwidth and the achieved diffraction efficiency, especially at the edges of the RF frequency band. The experiment revealed that the impedance matching is not completely correlated to the diffraction efficiency. Temperature measurements on the AOTF under test show that, at one edge of the tuning range, the RF signal is converted into a noninteracting acoustic mode.