An actively modelocked erbium fiber laser with continuous wavelength tuning over the range 1528 nm - 1565 nm has been demonstrated, with wavelength selection provided by a holographically ruled diffraction grating. A gain-saturated InGaAsP NTW semiconductor optical amplifier (SOA) is used as the active modelocking element in an isolating unidirectional fiber loop mirror. The semiconductor amplifier is driven with a synthesized RF signal source at a harmonic of the passive cavity mode spacing of 1.75 MHz, together with a dc bias current. The SOA is used as an amplitude modulator which provides gain and has < 2 dB polarization dependence. Gain saturation also serves to shape the transmitted laser pulses. The fiber laser is diode pumped at 1480 nm with a threshold of 6 mW, and provides pulses of 25 ps (FWHM) with a transform product of 0.4 and > 12 dBm peak power at a repetition rate of 175 MHz. Modelocked pulse repetition rates up to several GHz should be possible using this fiber laser configuration.