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 changing forest of “stuff” on the output.
Not the best thing for a “standard” ….. Bob > On Nov 12, 2016, at 4:24 PM, Gerhard Hoffmann <[email protected]> wrote: > > 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 goes to another SMA. > > The other half is to be dirtyfied. It is fed into another PSC2-1 that is > > used as a combiner. Its output goes to the signal source analyzer via > > a third SMA. > > > The dirt input is either a 4th SMA or a noise generator. That is switched > > by reed relays. The noise generator consists of a 60 Ohm resistor and > > currently 2 LMH6702 stages for +20 and +40 dB. I'm not sure if the > > 60R really defines the level, but the gain is at least flat from AF > > to > 100 MHz. If not yet, it can be made so. I have already a > > solid step attenuator so I can get rid of those reed relays. > > > I checked it this evening with my FE405 osc I bought earlier this year > > and that has enjoyed a good month of continuous running by now. > > I observed > > 1. that the FEI delivers only 3.5 dBm > > 2. that there are lots of birdies far out. Is that normal, maybe from the > DDS? > > > The addition of the noise reference lines seems to work properly. > > oscillator: > > < > https://www.flickr.com/photos/137684711@N07/30824608092/in/album-72157662535945536/ > > > > low calibration line: > > < > https://www.flickr.com/photos/137684711@N07/30824607162/in/album-72157662535945536/ > > > > high calibration line: > > < > https://www.flickr.com/photos/137684711@N07/30824607552/in/album-72157662535945536/ > > > > Later this evening I'll add the pic of the tin box. I need a USB cable... > > :-) Gerhard > > > _______________________________________________ > 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. _______________________________________________ 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.
