Brian Thanks for the details.
There are a number of problems with crystal filters. A crystal filter will have a finite bandwidth, and at offsets less than half the bandwidth the filter won't have a significant effect on the phase noise. For example the 40MHz xtal filter used in the 8662A has a bandwidth of 6kHz (according to the service manual), so phase noise at less than 3kHz offset will not be affected. For your application you would need a filter with a very narrow bandwidth indeed - maybe 50Hz or so. Ignoring the manufacturing issues of such a device, there could be problems with temperature sensitivity and microphony. These problems could of course be overcome, but I'm not convinced that a crystal filter would give an overall benefit in this application, given that the primary goal is to achieve leading-edge close in phase noise. The MSA1105 has better phase noise than I thought, but I'd still be tempted to change one or both of the passive doubler/buffer stages to an active doubler, if the figures for the NIST active doubler are correct. regards Grant _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
