Measurements are reported of electromagnetic emission close to the cyclotron frequency of energetic ions in JET plasmas heated by waves in the ion cylotron range of frequencies (ICRF). Hydrogen was the majority ion species in all of these plasmas. The measurements were obtained using a sub-harmonic arc detection system in the transmission lines of one of the ICRF antennas. The measured ion cyclotron emission spectra were strongly filtered by the antenna system, and typically contained sub-structure, consisting of sets of peaks with a separation of a few kHz, suggesting the excitation of compressional Alfven eigenmodes closely spaced in frequency. In most cases the energetic ions can be clearly identified as ICRF wave-accelerated He-3 minori...