The LNFR-100 is an ultra-low noise frequency reference. The LNFR-100 contains 5 MHz and 100 MHz ultra-low noise ovenized oscillators. The output at 10 MHz is obtained by multiplying the signal from the 5 MHz oscillator. The 100 MHz oscillator is phase locked to the 5 MHz oscillator to provide a lower phase noise signal inside the bandwidth of the phase-locked loop. The device can be used as a low noise source in phase noise measurement systems. Other applications include high stability frequency synthesizers, reference frequency generation and frequency synthesis chains for atomic standards. The LNFR-100 can be phase locked via a +/- 5 VDC tuning signal or with a 5 MHz 1 VRMS signal. This synthesizer is offered in a stand-alone rack-mount package. For frequency synthesis chain applications the synthesizer is available in modular form.