Since 2019, VGOS observations have routinely been carried out using the same frequency setup with a range from 3 to 10.7 GHz. Employing a network of European VGOS stations, we carried out experiments testing four alternative frequency setups covering the range between 3 and 14 GHz. The network consisted of antennas Onsala-East, Onsala-West, Santa Maria, Wettzell-South, and Yebes. The four new frequency ranges were 3000.4-13976.4, 4204.4-13964.4, 5004.4-13932.4, and 3000.4-13976.4 MHz. One important issue is the performance of the phase-cal signal, especially at the highest frequencies. We investigated the phase-cal signal by inspecting the raw data and by analyzing the signal extracted by the DiFX software correlator. Here we present our results concerning the quality of the phase-cal signal above 11 GHz. We conclude that phase-cal does not prevent VGOS observations at these high frequencies.