Hi Well, based on conversations with the people who designed the part, the outer oven’s only function was to take care of a potential cold end problem. At the time, the telecom guys were thinking of putting GPSDO’s in systems with no heating on the enclosures. That idea died when they ran into a variety of issues with the digital side of things at cold temperatures.
The issue isn’t the *sensitivity* as much as the simple fact that the 10811 will not warm up at all from a really cold temperature. There just isn’t enough heater power. If you want to dig into just why a “jacket” like this is not going to give you super oven performance, the various papers Rick published on his single oven are a good start. Bob > On Apr 8, 2020, at 3:53 PM, Jarl Risum <jarl.ri...@gmail.com> wrote: > > I have been puzzled by a mistake which has been published recently on this > list and elsewhere as well. It concerns the operation of the HP 10811 > double oven TCXO used in the HP Z3801 GPSDO. > > It is claimed that the outer oven is only in use during start up or during > extremely low ambient temperatures and is not operating during normal > conditions. This is not correct. > > The 10811 outer oven circuit in the HP Z3801 is designed to maintainin a > stable temperature around the 10811-60158 OCXO somewhere in the interval > between 60 and 65 deg. C in order to reduce the 10811-60158 OCXO's > sensitivity to temperature changes which – without the outer oven - is > specified as 4,5 x 10 e-9 from 0 to 71 deg. C. > > The HP Z3801 was made as a GPS disciplined timebase for synchronization of > CDMA Cellular Wireless Land Network base stations and was required to > maintain system syncronization for up to 24 hours in situations with > failure of GPS reception. In order to satisfy this requirement, the HP > Z3801's internal processor keep track of the gradual ageing of the 10811 > during normal GPS-disciplined operation and applies a calculated, predicted > correction voltage to keep the OCXO on frequency during periods with no GPS > signal (HP's Smart Clock technology). > > A diagram and detailed description of the 10811 outer oven circuit can be > found at KO4BB's manual collection under > http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=02_GPS_Timing/Z3801. > Pictures of the outer oven can be found at > www.realhamradio.com/GPS_Frequency_Standard.htm. > > In 2013 Warren Sarkison published an improved 10811 Outer Oven Controller > with improved temperature regulation. Description and numerous references > to his design can be found by Googling ”Warren S. Design 10811 Outer Oven > Controller”. This circuit - or something similar - is much to be > recommended if optimum operation of the dual oven 10811 outside of the HP > Z3801 is considered. > > Jarl > _______________________________________________ > 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.