Re: [time-nuts] Secondary phase noise standard & FE405

Hi The “sure fire” way to reduce the spurs is to go to a divisor that “fits” in to the DAC bit width. If you have a 12 bit dac, those points happen at Fclock / 2^12. For Time Nut sort of stuff that’s pretty coarse tuning. Bob > On Nov 13, 2016, at 11:03 AM, Tim Shoppa

Re: [time-nuts] Secondary phase noise standard & FE405

Some AD DDS app notes give examples of spurs and choosing nearby (but not exactly on freq) numbers that are much less bad for spurs - or at least that move the spurs outside the cleanup filters/loops. I don't know of a general example or even code that does this in a general way. One paper I like

Re: [time-nuts] Secondary phase noise standard & FE405

Hi > On Nov 13, 2016, at 2:55 AM, Gerhard Hoffmann wrote: > > Am 12.11.2016 um 23:52 schrieb Bob Camp: >> Hi >> >> Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS >> spurs come >> straight through. Since the FE-405 compensates for all sorts of

Re: [time-nuts] Secondary phase noise standard & FE405

Am 12.11.2016 um 23:52 schrieb Bob Camp: Hi Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS spurs come straight through. Since the FE-405 compensates for all sorts of things, the DDS moves around a lot. Even a one bit change on a DDS will move spurs around. With an

Re: [time-nuts] Secondary phase noise standard & FE405

Hi It depends both on the DDS “firmware” and the DAC linearity. You can play games to come up with the firmware side of it. The normal approach is to design the part so the DAC dominates. More or less, "more firmware bits” is cheaper than improving the DAC. Bob > On Nov 12, 2016, at 8:13

Re: [time-nuts] Secondary phase noise standard & FE405

kb...@n1k.org said: > Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS > spurs come straight through. Since the FE-405 compensates for all sorts of > things, the DDS moves around a lot. Even a one bit change on a DDS will move > spurs around. With an ever changing DDS,

Re: [time-nuts] Secondary phase noise standard & FE405

Hi Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS spurs come straight through. Since the FE-405 compensates for all sorts of things, the DDS moves around a lot. Even a one bit change on a DDS will move spurs around. With an ever changing DDS, you have an ever

[time-nuts] Secondary phase noise standard & FE405

I have made an experimental secondary phase noise standard, as F.Walls would call it. In the end, it's inspired by his paper. There is not much to it. There is a Mini Circuits PSC2-1 splitter that is fed from an oscillator or other source. The splitter divides it into a clean output that