The C-band 5 ~ 20 GHz picosecond fiber laser (PSL-10-TT) is an actively mode-locked fiber laser with continuously tunable repetition rate from 5 to 20 GHz that provides a stable and reliable optical clock with turnkey operation. Along with a portable design, the PSL-10-TT laser offers user-friendly front panel control knobs for flexible adjustment of wavelength, pulse width and output power. The wavelength can be tuned throughout the C-band. The pulse width can be tuned from 1.5 to 10 ps, with transform-limited spectral width and a better than -20 dB pedestal. The timing jitter is as low as 50 fs and the side mode suppression is better than -75 dB. An output power of greater than 20 mW obviates the need of an additional optical amplification stage. Options for 780 nm or 1 m band are also available.