Magnus Danielson wrote: > From: Predrag Dukic <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] Home built cesium clocks??? > Date: Sun, 29 Jun 2008 12:10:46 +0200 > Message-ID: <[EMAIL PROTECTED]> > > >> Bruce, >> >> I did my homework and collected everything from the internet I could >> get. I have this one too. >> >> If I go optical way, I still need 9+GHz electrical source, so I will >> first recreate electronics. Using off the shelf DDS chips, or using FPGA. >> > > A YIG oscillator or similar should be considered. The FPGA would be great > for the state handling, but be sure to externally reclock the signal > before use to remove the FPGA jitter. > > >> Also I need 9 GHz AOM, so that I can split the same optical beam and >> have two wavelengths 9ghz apart. That is a problem because I have >> only 350 MHz AOM. >> > > In the article he referenced, the AOM only needs to handle 250,1 MHz. > Only if you intend to achieve 100% pumping and detection ratios you need > a full set of frequencies. Notice the important note on relation between > laser linewidth and S/N relationship. Luckilly those are limitations > outside of the cavity. > > The interesting aspect with an optically pumped cesium is that one of the > common failuremodes, the contamination of the masspectrometer is removed. > The detection is off-axis from the beam. Wonder if an open oven could not > be installed there. That would allow for a ping-pong mode of operation, > which the optical pumping itself fits very nicely too. It would cancel > some of the systematic shifts due to assymetries in the microwave > assembly which to the best of my knowledge is hard to compensate normally. > Maybe state of art designs have found a way to handle it properly. > > >> Multiple pass is difficult, it would take cca 27 passes to get 9 >> GHz. On the other side, I wouldn't need the last stages of SRD >> multiplication to get 9 GHz microwave. >> >> No doubt, I will have a lot of fun with the project. >> > > Surely. It could be hairpulling too. > > Cheers, > Magnus > > Even PTB's CSF2 caesium fountain doesn't require a 9 GHz AOM: http://tycho.usno.navy.mil/ptti/ptti2005/paper29.pdf
If one starts with a low noise 9GHz oscillator and divides down to a suitable PLL loop frequency using regenerative multipliers then SRD multipliers arent required. Alternatively if you can still find a suitable NTL multiplier they are somewhat quieter than SRDs. Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.