For us it is absolute Frequency, to me it is a measure of true performance. In a message dated 9/1/2016 4:52:35 P.M. Eastern Daylight Time, kb8tq@n1k.org writes: Hi I think one issue here is that ADEV is being used by one “lab" and absolute frequency is being used by the other. They very much are *not* the same thing. There isn’t even a really simple way to convert one to the other. There will always be a big delta between those two measures. For absolute frequency you will also need some sort of confidence number (99 % or some such thing). The details of why all this happens are the mainstay of the 1960’s (and early 70’s) papers on ADEV. Bob > On Sep 1, 2016, at 3:11 PM, Tom Van Baak <tvb@LeapSecond.com> wrote: > > Hi Bert, > >> because the frequency is constantly changed to correct time. > > A simple answer: you may have a bad TBolt. Was it part of the TAPR group buy, or did you buy it from eBay/China? If TAPR, you get a free replacement. Contact me off-list. > >> Tbolt is an excellent time device but not good for frequency reference past 1E-10. > > No, again it sounds like you have a bad TBolt. Or something is wrong (antenna? reception? time constant? environment? China resoldered parts?). I appreciate that Juerg did lots of testing -- do you happen to have his ADEV plot? > > I'm willing to help you debug this. > > (1) Attached is the ADEV of 8 random TBolts that I tested recently. How does this compare to yours? You can see mine are all under 2e-12 at 1 s and under 4e-12 at 100 s. On a bad day during holdover it might climb to 1e-11 at 1000 s but when locked GPS disciplining takes over and keeps it down to 2 or 3e-12. > > (2) For locked vs. unlocked TBolt ADEV, see http://www.leapsecond.com/pages/gpsdo/ > > (3) Also attached is a frequency plot showing the typical noise and wander, down at the 1e-11 level. How does this compare with yours? > > Your claim of 1e-10 is order(s) of magnitude worse than the TBolts that I see. Something is wrong. > > /tvb > > ----- Original Message ----- > From: "Bert Kehren via time-nuts" <time-nuts@febo.com> > To: <time-nuts@febo.com> > Sent: Thursday, September 01, 2016 9:54 AM > Subject: [time-nuts] Tbolt issues > > >> We have been following the Tbolt power discussions but what I am missing is >> the main problem with Tbolts. All the power work will not improve the >> frequency performance of the unit because the frequency is constantly changed >> to correct time. Tbolt is an excellent time device but not good for >> frequency reference past 1E-10. I noticed it when I bought it and compared it with >> my Tracor 527E on the needle and ever since used an Austron 2110 with a >> digital 100 sec. loop for clean up. My Swiss partner Juerg has relied on an >> OSA F3 for Tbolt clean up but continuous bad results on our work resulted in >> a detailed analysis using a HP53132A counter and M100, FTS44060, two >> OSA8600's and one of the best FE405's. The rsult is that the OSA F3 does not >> clean up the Tbolt and we see +-4E-11 changes and old data shows even some +-8 >> E-11 excursions. With the popularity of the Tbolt an analog or digital >> clean up loop would make sense. We are working on both, the analog because I >> saw similar behavior on the FE5680 and FE5650, we did a GPSDO but do not plan >> on using those Rb's but focus on M100 and FRK. >> The collective expertise of time nuts could make a significant contribution >> For power in critical applications we use the excellent work from Bern Kaa >> a friend for the last twenty years and well known because of his published >> work in the European HAM community >> Bert Kehren > <TBolt8-1.gif><TBolt8-2.gif>_______________________________________________ > 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. _______________________________________________ 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.