STE-SF419-S1 is a U-Band X4 frequency extender that uses an input frequency range of 10 to 15 GHz at +0 dBm along with harmonic generation and filtering to produce a 40 to 60 GHz RF signal. The extender features an adjustable attenuator for output power control. The extender is designed and manufactured as a bench top unit to extend the low frequency synthesizer or sweeper such as Eravant models STL-SG-022203-S1 or SOT-02220313200-SF-B6, without losing all of the functionalities and features. The extender also features adjustable legs, which can also be removed, to allow for an easy test set up.