We report the gigahertz experimental results of time and frequency performance on YBCO high temperature superconductor (HTS) and gold coplanar transmission lines. An on-wafer direct probing measurement system was used to collect data at cryogenic temperatures on both YBCO and gold coplanar lines. The insertion loss of the 6-cm lines at a frequency of 3.0 GHz was measured to be -0.12 dB for the superconducting line compared to -10.7 dB for the gold line at 80 K. Error rate and eye-diagram measurements were performed on the packaged lines and show the correlation between the insertion loss of the line and the attenuation of a Pseudo Random Bit Sequence (PBRS). The superconducting line measured at 77 K had a BER rate of less than 10/sup -11/ at a data rate of 3 Gb/s. The measured eye height was 350 mV for the YBCO compared to 100 mV for a gold line at 3 Gb/s and a temperature of 77 K for the packaged 6-cm lines.