Charles, I don't know the answer to that question. Since it's a thermal issue, it's a question of how long does it take for the temperature to stabilize? 24 hrs. should be lots of time. I'd check it before going to bed. A quick turn-on and measure won't raise the temperature much and will quickly show if there's a change from normal. And, as mentioned, it takes mine about 2 hrs. to stabilize after being turned back on. Ed On 12/18/2011 4:35 PM, Charles P. Steinmetz wrote: > Ed wrote: > >> Agreed. But it was annoying to leave it in standby mode and then >> still have some drift. At first, I thought the drift was due to the >> rest of the unit warming up. I was quite surprised when my tests >> showed that the drift was 100% due to the oscillator. Using an FRK >> as an external reference, I can turn on my 1992 (not from standby) >> and immediately measure my Z3801A as 10.000 000 000 MHz. > > I put one of mine in standby earlier this afternoon. I'll turn it > back on tomorrow afternoon and report the results. How long does > yours have to be in standby before it comes on 40 counts off? > > Best regards, > > Charles >

My Racal1994 oscillator is labeled "9462 454879" on one face of the can and "404386C" on another. Aart Olsen ----- Original Message ----- From: "Charles P. Steinmetz" <charles_steinmetz@lavabit.com> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Sunday, December 18, 2011 12:00:58 PM Subject: Re: [time-nuts] My Racal-Dana 1992 There are actually two Racal part numbers that you sometimes see in documentation as being used for Option 04E -- 404386 and 454879. The 9462s in the US military contract 1992s that I have seen (pretty much all of the 1992s one sees in the US are from the mil contract, IME) are marked "9462 454879." I have not seen an oscillator marked "404386," so I do not know if these are Model 9462 oscillators or another model.

I wrote: >I put one of mine in standby earlier this afternoon. I'll turn it >back on tomorrow afternoon and report the results. (All results using 10 second gate): Yesterday, the 1992 had been reading "000.000000 E-3" stably for several days, and I switched it to standby. After 16 hours in standby, it came on 4 counts (4 mHz) high, rose to 9 counts high in 5 minutes, hung there for about 15 minutes, then slowly came down to 0 over the next hour. It undershot 0 by the tiniest bit (several minutes of occasionally reading "999.999999 E-3". It has been reading 0 stably for over 3 hours now. So, mine also has an error with a long time constant when it comes out of standby, but of lesser magnitude than Ed's (peak error 9x10 E-10). I presume the magnitude of the error may change with ambient temperature (in my case, 74.1 F throughout). Chuck speculated several days ago that the 9462 fine adjustment may be an oven parameter (temperature?) adjustment. The long, oscillatory nature of the settling when the fine adjustment is changed does suggest the action of a somewhat underdamped control loop. Both the ringing and the long time constant tend to support the oven temperature hypothesis (but I am still reluctant to believe they would design a frequency adjustment this way). Best regards, Charles

Charles, My restart followed the same pattern as yours. Start high, go higher, drift down, undershoot, recover. The start was 10 MHz +51 counts, rise to +60 counts after 5 minutes, drift down to a minimum of +8 counts after 90 minutes and recover to +11 counts after 10 more minutes for a total shift of -40 counts (peak error of 4e-9). I'm going to redo all these tests, but I think I'll be sticking to the external standard. Ed On 12/19/2011 12:33 PM, Charles P. Steinmetz wrote: > I wrote: > >> I put one of mine in standby earlier this afternoon. I'll turn it >> back on tomorrow afternoon and report the results. > > (All results using 10 second gate): Yesterday, the 1992 had been > reading "000.000000 E-3" stably for several days, and I switched it to > standby. After 16 hours in standby, it came on 4 counts (4 mHz) high, > rose to 9 counts high in 5 minutes, hung there for about 15 minutes, > then slowly came down to 0 over the next hour. It undershot 0 by the > tiniest bit (several minutes of occasionally reading "999.999999 > E-3". It has been reading 0 stably for over 3 hours now. > > So, mine also has an error with a long time constant when it comes out > of standby, but of lesser magnitude than Ed's (peak error 9x10 E-10). > I presume the magnitude of the error may change with ambient > temperature (in my case, 74.1 F throughout). > > Chuck speculated several days ago that the 9462 fine adjustment may be > an oven parameter (temperature?) adjustment. The long, oscillatory > nature of the settling when the fine adjustment is changed does > suggest the action of a somewhat underdamped control loop. Both the > ringing and the long time constant tend to support the oven > temperature hypothesis (but I am still reluctant to believe they would > design a frequency adjustment this way). > > Best regards, > > Charles > >

This is typical for an underdamped second order servo. The oscillation is the penalty for a shorter settling time. A critically damped system would not oscillate, but approach the final value smoothly in a slightly longer time. It may have been designed for a slight overshoot... Don Ed Palmer > Charles, > > My restart followed the same pattern as yours. Start high, go higher, > drift down, undershoot, recover. The start was 10 MHz +51 counts, rise > to +60 counts after 5 minutes, drift down to a minimum of +8 counts > after 90 minutes and recover to +11 counts after 10 more minutes for a > total shift of -40 counts (peak error of 4e-9). I'm going to redo all > these tests, but I think I'll be sticking to the external standard. > > Ed > > On 12/19/2011 12:33 PM, Charles P. Steinmetz wrote: >> I wrote: >> >>> I put one of mine in standby earlier this afternoon. I'll turn it >>> back on tomorrow afternoon and report the results. >> >> (All results using 10 second gate): Yesterday, the 1992 had been >> reading "000.000000 E-3" stably for several days, and I switched it to >> standby. After 16 hours in standby, it came on 4 counts (4 mHz) high, >> rose to 9 counts high in 5 minutes, hung there for about 15 minutes, >> then slowly came down to 0 over the next hour. It undershot 0 by the >> tiniest bit (several minutes of occasionally reading "999.999999 >> E-3". It has been reading 0 stably for over 3 hours now. >> >> So, mine also has an error with a long time constant when it comes out >> of standby, but of lesser magnitude than Ed's (peak error 9x10 E-10). >> I presume the magnitude of the error may change with ambient >> temperature (in my case, 74.1 F throughout). >> >> Chuck speculated several days ago that the 9462 fine adjustment may be >> an oven parameter (temperature?) adjustment. The long, oscillatory >> nature of the settling when the fine adjustment is changed does >> suggest the action of a somewhat underdamped control loop. Both the >> ringing and the long time constant tend to support the oven >> temperature hypothesis (but I am still reluctant to believe they would >> design a frequency adjustment this way). >> >> Best regards, >> >> Charles >> >> > > _______________________________________________ > 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. > -- "Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind." R. Bacon "If you don't know what it is, don't poke it." Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com