Hi The first gotcah is that the distinction is not very clear. A TBolt varies the frequency of the OCXO in the GPSDO. GPSDO’s that use Rb’s can and often do vary the frequency.
Indeed some devices use a DDS to generate an output rather than varying something else. I suspect that is what you are bumping into. In some cases a DDS feeds a cleanup loop or filter that restricts the output range. If you are after low noise at 10 GHz, the multiplier chain needs to be carefully designed. There is a lot more to it than you might think. The first and most basic question would be “is it a fixed frequency output or tuned?”. From there you can head off in a number of directions. If you need to be able to change frequency from 1 MHz to 10 GHz in a few nanoseconds, then there is no alternative to using a DDS. If hat is part of the requirement then you go from there. If you want only 10 GHz +/- 0.001Hz then there are other, more quiet / lower spur ways to do the job. Indeed it goes on and on ….. Bob > On Sep 25, 2019, at 4:45 PM, Taka Kamiya via time-nuts > <[email protected]> wrote: > > This is a cross post from EEVBLOG. I'm hoping there is someone who's > familiar with this subject would help me out here. > I am hoping someone can help me understand this. I've seen similar > discussions take place both for GPSDO with Crystal Oscillators and Rubidium > modules. It appears there are two types of each. > 1) fixed frequency type (less jitter) > 2) frequency agile type (more jitter) > > I've read frequency agile Rb modules (ones you can change output frequency) > is one kind of Rb (sa.22c and fe5650, etc), and there is another one that you > cannot change frequency. (ie. T-bolt, PRS10, etc). Words like phase noise > and PLL are thrown out often in discussions. I vaguely remember frequency > agile types are less suitable if ultimate in stability is needed such as > multiplying the output into GHz range. This discussion was about 10GHz > transverter. > Is this because frequency agile type has the ultimate output from PLL > (subject to jitter) and fixed frequency type is from OCXO? If this is the > case, why frequency agile type even exist? It's not like it can be used as a > VFO (on radio)..... > > I'm sorry this is SO vague but that's the reason for this post. I need to > understand this. There was a wiki page on this, but it doesn't go into this > discussion deep enough. > > Would someone help me gain knowledge in this? > > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
