J. Freed,

I took Phase noise measurements of the 2 channel Keysight 33600A waveform generator for its use in building SPI Pathfinder in the optics lab before install. Going only off of the phase noise graphs, it is sufficient as it shows comparable results to the SRS which had a phase noise considered to be good enough for SPI pathfinder.

Key.png Shows the phase noise results. C1, C2 are the phase noise results for Channel 1 and Channel 2 on the Keysight, respectively. (Set up shown below). Shown for comparison the SRS SG392, which was suggested as a possible frequency source for SPI. The last measurement shown is the direct measurement of phase noise between the 2 channels of the Keysight. This measurement reflects the intended use case of the Keysight for SPI. As we need 2 frequencies at slightly different frequencies locked to each other and SPI will be measuring the output phase difference. Note the 60Hz peak; most likely caused by unclean AC power. This is why we are not using an AC powered device in the final installation. 

Screenshot2025-12-01at50150 PM.png Shows the setup for C1, and C2. measurements. The SRS value was found with the same set up, just replacing the Keysight 33600A with a SRS. The C1-C2 is a direct measurement by plugging both channels into the BluePhase 1000. There is no 10MHz Ext back attachment in this measurment in order to best represent Keysight's theoretical performance in the optics lab.