Hi Indeed the outer oven (as a minimum) needs to be 5 to 10 C above the maximum ambient. If it’s not it goes out of regulation (runs away) and you loose any benefit from it. ( = it now works against you ).
The inner oven as a minimum needs to be 5 to 10 C above the outer oven. Again if it is lower, you can / will get into the same runaway issue. Those offsets are dependent on the way things are insulated. If you are using a dewar flask, 5C is probably not going to work for you. Your inner oven *also* is impacted by the turn temperature on the crystal being used. This *might* have a 20C range. That would put the maximum inner oven temperature at 10 + 10 + 20 = 40C above the maximum ambient. Needless to say, if the max ambient is 85C, this will get the inner oven components up pretty hot. That’s not a real good idea. Derating the heater is pretty easy, derating *everything* in there is much more complex. You do not often see 85C upper end double ovens …. One *could* also ask: “is all this worth it?”. List members *have* written papers addressing that point :) Bob > On Feb 11, 2021, at 10:05 PM, Paul Alfille <[email protected]> wrote: > > Shouldn't the outer oven be cooler than the inner oven except during > warmup? I would think the inner electronics would be generating heat. > > Paul Alfille K1PHA > > On Thu, Feb 11, 2021 at 9:30 PM paul swed <[email protected]> wrote: > >> 50C is what I have sort of seen over the years. Just wondered could there >> have been a lower temp version. That made no sense. But then this beast has >> never made a lot of sense. The $20 mystery from Frequency Electronics. >> Thanks Bob >> Paul >> WB8TSL >> >> On Thu, Feb 11, 2021 at 8:08 PM Bob kb8tq <[email protected]> wrote: >> >>> Hi >>> >>> Even for an outer oven, anything below 60C / 140F would be low enough to >>> run into significant problems. On a mil device, an upper end temperature >>> on >>> the equipment likely would be over 70C. The outer oven would need to be >>> 5 to 10C above that. >>> >>> Bob >>> >>>> On Feb 11, 2021, at 5:55 PM, paul swed <[email protected]> wrote: >>>> >>>> OK I have had several responses and 110F is low as I expected. >>>> Wonder if I am being faked out? Perhaps by an inner oven and I am only >>>> reading the outside of the outer oven. The Older URQ10 and newer URQ23 >> do >>>> have 2 ovens. The meter switch for test is only labeled 1-9. no other >>> clues >>>> to the function. I noticed 2 positions change with warm up. Sort of >>>> supports the 2 oven theory. >>>> Really do not want to take what might be the outer oven off to put the >>>> probe in. >>>> Thanks everyone. >>>> Paul >>>> WB8TSL >>>> >>>> On Thu, Feb 11, 2021 at 5:32 PM Bob kb8tq <[email protected]> wrote: >>>> >>>>> Hi >>>>> >>>>> 110 F makes very little sense unless you are in a very cold climate. >>>>> For military gear (or any gear for that matter) 43C on the oven just >>>>> doesn’t work. >>>>> >>>>> 110 C would make sense in a very high temperature environment. >>>>> (think of 85C upper end ….). >>>>> >>>>> Bob >>>>> >>>>>> On Feb 11, 2021, at 2:18 PM, paul swed <[email protected]> wrote: >>>>>> >>>>>> Hello to the group. >>>>>> I have had a AN/URQ-13 or FE-15a oven oscillator for years. >>>>>> Its never worked correctly and in reality some early alpha build. >>> (Funny >>>>>> that its labeled 15a) >>>>>> Looking online there is no documentation that I have been able to >> find >>>>> over >>>>>> the years. >>>>>> However in another discussion on a AN/URQ-23 that does have a manual >>> and >>>>>> schematics I realized my guesses on power could be totally wrong. >> Using >>>>>> voltages like the URQ23 the URQ13 actually behaves fairly well. I was >>>>> lucky >>>>>> that I didn't destroy something with my original guess. >>>>>> That said what I find odd is the internal crystal oven runs at >> exactly >>>>> 110 >>>>>> degrees. Its repeatably warms to that level with a range of supply >> from >>>>> +/- >>>>>> 12-15V. >>>>>> Does 110 degrees F make any sense at all? >>>>>> Thank you >>>>>> Paul >>>>>> WB8TSL >>>>>> _______________________________________________ >>>>>> 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. >>>>> >>>> _______________________________________________ >>>> 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. >>> >> _______________________________________________ >> 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. _______________________________________________ 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.
