Bob FWIW, I have found in designing stuff like this over the years, that for customer satisfaction (utility, aerospace, commercial., mil, consumer) go one order magnitude better than final specs require ( 10 orders for mil).
So if better than +/- 1 Hz is required, design the SYSTEM(s) for better than +/- 0.1 Hz, guarranty +/- 1 Hz and there can be no quibling over accuracy down the road. Phil, K3IB ----- Original Message ----- From: "Robert McGwier" <[EMAIL PROTECTED]> To: "ecellison" <[EMAIL PROTECTED]> Cc: <FlexRadio@flex-radio.biz>; "Jim Lux" <[EMAIL PROTECTED]> Sent: Sunday, November 27, 2005 9:04 AM Subject: Re: [Flexradio] ebay 10MHz-OCXO- > Eric: > > This has 0.9 ppm stability. That means it will move about and the range > is 9-ish Hz or less guaranteed. Alberto's needs would not be met by > this part. However, most people's needs <would> be met by this part > and steering this oscillator to much better stability that 0.9 ppm is > very do-able. Rick Hambly has two oscillators in his CNS-II clocks. > One is a $12-ish part and one is a Valpey-Fisher expensive TCVCXO. The > $12 part with the PIC tuning alrogithm, does a part in 0.001 ppm easily > with GPS tamed steering. The Valpey-Fisher (I think I own all but one > of those clocks anyway) is much better but we just do not need this. > Again, the design goal is determined by what it is you are trying to > achieve. Rick's clocks have a proprietary difference we won't go into > here but the point his you can steer that $12 oscillator to under 1 Hz > accuracy with good stability pretty easily. > > What frequency accuracy do you (all of you) really want with the > SDR-1000 (say)? 1 Hz at 50 Mhz is 2 part in 10^8. That is doable with > the $12 oscillator with steering with the properly designed time > constants. Don't expect to hold it to 0.001Hz because you will exceed > the tracking range/rate of the closed loop system. > > From Alberto's comments , he is expecting much higher performance than > this and can get it with his work. It is my assertion that the worst > mistake we can make is to over-engineer this when it is absolutely not > needed. We want Ross Biggar to be able to tune his radio to frequency > 14.111123 and be under 0.5 Hz off so Olivia works immediately. We want > Mike King to be able to tune his 10 Ghz equipment and be absolutely > certain that any error is mainly attributable to the external > transverter LO's. > > Bob
