The Hewlett-Packard Model 511DA Synthesizer Driver is part of a frequency synthesizer system consisting of the 5110A and the Hewlett-Packard Model 5100A Frequency Synthesizer. The Synthesizer Driver provides the 22 fixed frequencies necessary to drive the 5100A. The Driver derives all these frequencies from an internal 1 Me frequency standard which is stable to ±3 parts in 109 per day. The filtered 1 Me signal is fed to a comb or harmonic generator. Immediately after the harmonic generator, the third harmonic is filtered off, amplified, and refiltered. The remainder of the harmonic rich signal is passed through a 24 to 39 Me bandpass filter, amplified, and then fed to active filtering, synchronously tuned transistor-tank stages which select out the 24 Me and 30 through 39 Me components. The filtered components lying between 30 Me and 39 Me are also fed to frequency dividers to provide the low frequency spectrum output of 3.0, 3.1, 3.2, 3. 3, 3. 4, 3. 5, 3. 6, 3. 7, 3.8, and 3. 9 Me. The 5110A thus provides the 5100A Frequency Synthesizer, by means of rear panel BNC connectors, very stable and clean signals of 3 Me, 24 Me, 3.0 through 3.9 Me in 100-kc steps, and 30 through 39 Me in 1 Me steps.