  We start an environmentally-stable linear Mamyshev oscillator with
electronically-controlled modulated pump and a moving filter. It delivers a
21-nJ pulse that becomes 65 fs in duration after a compressor. Reliable
starting into stable mode-locking is found achievable with a modulated
mode-locked state observed only when the modulation frequency is larger than 70
kHz. To avoid the damage of the gain fiber, two Faraday rotators are
introduced. Besides, we have studied several aspects toward obtaining
successful starting.
