Hi, There is actually more approaches. Me and NIST showed you can setup a cross-correlating interferometer, it actually works, but is so far hard to maintain properties, but the principle works so we presented and published it.
Another approach suggested by Enrico is to actually compensate with the expected noise-level of the power-divider resistor, and you do not need to match that extremely well to cover most of the noise. Yet another being used when you do not need to go all the way down is to have a common resistor and then use active buffers for power-splitting. It's not perfect and there will be a common mode noise that remains, but it will be robust to cancellation due to power-splitter noise of anti-correlation, so for many purposes this is good enough. Thus, there is three different methods to work around it and one pragmatic to dodge it. So you can avoid cryogenic methods, but none of these methods is perfect, we have not solved it completely. Cheers, Magnus On 2019-08-21 11:16, Bruce Griffiths wrote: > That should have been: > > Its only necessary (as NIST have shown) to cool the splitters to reduce the > correlated or anti-correlated thermal noise between splitter outputs. > Everything else can run at ambient temperature. > > Bruce > >> On 21 August 2019 at 21:13 Bruce Griffiths <bruce.griffi...@xtra.co.nz> >> wrote: >> >> >> Its only necessary (as NIST have shown) to cool the splitters to reduce the >> correlated or anti-correlated noise between the outputs. Everything else can >> run at ambient temperature. >> >> Bruce >>> On 21 August 2019 at 18:49 ed breya <e...@telight.com> wrote: >>> >>> >>> That's quite an impressive system. I guess it's a few generations beyond >>> my 11729C. >>> >>> One way to get overall performance to the limits of room temperature kT >>> noise level, is to lower the T where you work. I wouldn't be surprised >>> if some parts are TE-cooled, easily affordable in a big budget system. >>> My first thought was maybe a bunch of stuff in a cryogenic system, but >>> it looks like most pieces are modules in a rack mainframe, and not in a >>> special environment. But, within the modules, I could picture some >>> degree (PTP) of TE-cooling being included, giving some margin on the >>> capabilities. >>> >>> Ed >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
