[time-nuts] Re: Thunderbolts
Hi Trimble mentions the E oscillator in a couple of places. They also seem to only talk about holdover in very vague terms. They never tie down anything that would track back to the stability of the OCXO. If it *is* a high(er) performance OCXO, I find that all a bit weird. The ADEV plot they show looks a lot like the fine old TBolt we all know and love …. Bob > On Jul 21, 2021, at 9:48 AM, Dana Whitlow wrote: > > Bob, I'm aware of the hump, but it's so much smaller than what I see from > GPSDO that > I don't mind it too much. > > My current usage scenario is that I use one or more GPSDOs as a reference > for > tweaking one of my Rb stds to reasonable conformance with GPS. Frequency > noise on either gets in the way of doing this most accurately, and greatly > extends > the observation time required to do a good tweak job. I "observe" with the > aid of > a home-built quadrature demodulator and a duan-channel DSO running in very > slow "roll mode", with its two channels driven by I & Q outputs of the > demod. > Thus I can learn a lot just by an occasional glance at the display as I > happen > to pass near the 'scope in the course of other activities. > > I currently own a new CNS *Clock II* and three older T'Bolts. The CNS unit > has a very fast > tracking loop, with an estimated time constant of only a very few seconds > (not user- > adjustable). It's 10 MHz output is incredibly noisy, with > frequent frequency excursions > of several PPB either way. But at least it does not have much trouble with > ambient > temperature sensitivity. The T'Bolts have user-adjustable time constant, > and I've > spent a lot of time playing with those. For very short TC settings the GPS > noise dominates > the picture, and for very long settings ambient temperature fluctuations on > the GPSDO's > VCXO dominate. I keep going back to the CNS clock because although its > frequency > fluctuations are more severe, I find it's easier to visually estimate tweak > amounts. > > My desire is to maintain an Rb within 10 PPT most or all of the time with > little or no > manual attention. > > In response to your latest, I'm sure I saw mention of a double-oven in > connection with the > T'Bolt E, on the Trimble site. But perhaps this is an extra cost option. > Thanks for mentioning > this. > > As an amusing side note I occasionally rely on a local taxi service, and > one of the regular > drivers' last names is Trimble. Perhaps I should inquire if there is any > connection :-) > > Dana > > > On Wed, Jul 21, 2021 at 8:20 AM Bob kb8tq wrote: > >> Hi >> >> With the PRS-10 you get that hump in the ADEV. I’m not saying that it’s >> the >> end of the world, but it really does bug me that it’s there …. >> >> Bob >> >>> On Jul 20, 2021, at 10:03 PM, Dana Whitlow >> wrote: >>> >>> Bert, remember that I need a very long locking loop time constant >> setting in >>> order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a >>> holdover state anyway, all the time. >>> >>> Probably the smartest thing for me to do is to buy a spanking new PRS-10, >>> with the PPS locking feature present. Then I could just leave it locked >> to >>> GPS most all the time, but disconnect the PPS and let it go into holdover >>> on the rare occasions when I need a few hours of even better stability. >>> >>> Dana >>> >>> >>> On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts < >> time-nuts@lists.febo.com> >>> wrote: >>> There is a lot of misinformation out there. It is not the OCXO that changes, Bruce did extensive testing and I did some too. The Vectron is super, would like to know what is in it but do not want to open one. >> Once warmed up the stable OCXO temperature is a main contributor to the board temperature. Using a Dual Oven may give you a warm feeling but only >> adds 1 more Watt of stable heat to the board making the temperature change smaller. The OCXO is important during Hold Over and that is why it is there. The changes are the DAC which is updated once a second. Very temperature sensitive. Cheap. We have done the tests 10811, OSA 8600, >> FRK and M100. For fun did use a cheap small OCXO, no performance change. Was done in Juerg's temperature stable basement. See attached picture. Bert Kehren My experiences with the T'Bolt have not been entirely satisfactory. If >> I set the loop lime constant long enough to get a satisfying smoothing of the GPS >> noise (a few hundred seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears >> its ugly head and I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly >> has a double- oven XO, so I'd like to give that a try. But my wallet says "whoa"! According to Bodnar, his units do have some choices in the time constant setting. I've been considering ordering a Bodnar
[time-nuts] Re: Thunderbolts
Bob, I'm aware of the hump, but it's so much smaller than what I see from GPSDO that I don't mind it too much. My current usage scenario is that I use one or more GPSDOs as a reference for tweaking one of my Rb stds to reasonable conformance with GPS. Frequency noise on either gets in the way of doing this most accurately, and greatly extends the observation time required to do a good tweak job. I "observe" with the aid of a home-built quadrature demodulator and a duan-channel DSO running in very slow "roll mode", with its two channels driven by I & Q outputs of the demod. Thus I can learn a lot just by an occasional glance at the display as I happen to pass near the 'scope in the course of other activities. I currently own a new CNS *Clock II* and three older T'Bolts. The CNS unit has a very fast tracking loop, with an estimated time constant of only a very few seconds (not user- adjustable). It's 10 MHz output is incredibly noisy, with frequent frequency excursions of several PPB either way. But at least it does not have much trouble with ambient temperature sensitivity. The T'Bolts have user-adjustable time constant, and I've spent a lot of time playing with those. For very short TC settings the GPS noise dominates the picture, and for very long settings ambient temperature fluctuations on the GPSDO's VCXO dominate. I keep going back to the CNS clock because although its frequency fluctuations are more severe, I find it's easier to visually estimate tweak amounts. My desire is to maintain an Rb within 10 PPT most or all of the time with little or no manual attention. In response to your latest, I'm sure I saw mention of a double-oven in connection with the T'Bolt E, on the Trimble site. But perhaps this is an extra cost option. Thanks for mentioning this. As an amusing side note I occasionally rely on a local taxi service, and one of the regular drivers' last names is Trimble. Perhaps I should inquire if there is any connection :-) Dana On Wed, Jul 21, 2021 at 8:20 AM Bob kb8tq wrote: > Hi > > With the PRS-10 you get that hump in the ADEV. I’m not saying that it’s > the > end of the world, but it really does bug me that it’s there …. > > Bob > > > On Jul 20, 2021, at 10:03 PM, Dana Whitlow > wrote: > > > > Bert, remember that I need a very long locking loop time constant > setting in > > order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a > > holdover state anyway, all the time. > > > > Probably the smartest thing for me to do is to buy a spanking new PRS-10, > > with the PPS locking feature present. Then I could just leave it locked > to > > GPS most all the time, but disconnect the PPS and let it go into holdover > > on the rare occasions when I need a few hours of even better stability. > > > > Dana > > > > > > On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts < > time-nuts@lists.febo.com> > > wrote: > > > >> There is a lot of misinformation out there. It is not the OCXO that > >> changes, Bruce did extensive testing and I did some too. The Vectron is > >> super, would like to know what is in it but do not want to open one. > Once > >> warmed up the stable OCXO temperature is a main contributor to the board > >> temperature. Using a Dual Oven may give you a warm feeling but only > adds 1 > >> more Watt of stable heat to the board making the temperature change > >> smaller. The OCXO is important during Hold Over and that is why it is > >> there. The changes are the DAC which is updated once a second. Very > >> temperature sensitive. Cheap. We have done the tests 10811, OSA 8600, > FRK > >> and M100. For fun did use a cheap small OCXO, no performance change. Was > >> done in Juerg's temperature stable basement. See attached picture. > >> > >>Bert Kehren > >> My experiences with the T'Bolt have not been entirely satisfactory. If > I > >> set the loop > >> lime constant long enough to get a satisfying smoothing of the GPS > noise (a > >> few hundred > >> seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears > its > >> ugly head and > >> I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly > has > >> a double- > >> oven XO, so I'd like to give that a try. But my wallet says "whoa"! > >> > >> According to Bodnar, his units do have some choices in the time constant > >> setting. > >> I've been considering ordering a Bodnar just for frequency agility, but > >> have been > >> holding off out of concern for the complications of dealing with a > foreign > >> supplier. > >> > >> Dana > >> ___ > >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send > >> an email to time-nuts-le...@lists.febo.com > >> To unsubscribe, go to and follow the instructions there. > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send an email to
[time-nuts] Re: Thunderbolts
Hi All of the Thunderbolt E’s that I have seen have single oven OCXO’s. I don’t know of any “current production” GPSDO’s that come stock with double ovens. There are a few with some interesting options. I have not dug into just what all those odd options actually are. Bob > On Jul 20, 2021, at 7:55 PM, ew via time-nuts > wrote: > > There is a lot of misinformation out there. It is not the OCXO that changes, > Bruce did extensive testing and I did some too. The Vectron is super, would > like to know what is in it but do not want to open one. Once warmed up the > stable OCXO temperature is a main contributor to the board temperature. Using > a Dual Oven may give you a warm feeling but only adds 1 more Watt of stable > heat to the board making the temperature change smaller. The OCXO is > important during Hold Over and that is why it is there. The changes are the > DAC which is updated once a second. Very temperature sensitive. Cheap. We > have done the tests 10811, OSA 8600, FRK and M100. For fun did use a cheap > small OCXO, no performance change. Was done in Juerg's temperature stable > basement. See attached picture. > > Bert Kehren > My experiences with the T'Bolt have not been entirely satisfactory. If I > set the loop > lime constant long enough to get a satisfying smoothing of the GPS noise (a > few hundred > seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its > ugly head and > I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly has > a double- > oven XO, so I'd like to give that a try. But my wallet says "whoa"! > > According to Bodnar, his units do have some choices in the time constant > setting. > I've been considering ordering a Bodnar just for frequency agility, but > have been > holding off out of concern for the complications of dealing with a foreign > supplier. > > Dana > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Thunderbolts
Hi With the PRS-10 you get that hump in the ADEV. I’m not saying that it’s the end of the world, but it really does bug me that it’s there …. Bob > On Jul 20, 2021, at 10:03 PM, Dana Whitlow wrote: > > Bert, remember that I need a very long locking loop time constant setting in > order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a > holdover state anyway, all the time. > > Probably the smartest thing for me to do is to buy a spanking new PRS-10, > with the PPS locking feature present. Then I could just leave it locked to > GPS most all the time, but disconnect the PPS and let it go into holdover > on the rare occasions when I need a few hours of even better stability. > > Dana > > > On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts > wrote: > >> There is a lot of misinformation out there. It is not the OCXO that >> changes, Bruce did extensive testing and I did some too. The Vectron is >> super, would like to know what is in it but do not want to open one. Once >> warmed up the stable OCXO temperature is a main contributor to the board >> temperature. Using a Dual Oven may give you a warm feeling but only adds 1 >> more Watt of stable heat to the board making the temperature change >> smaller. The OCXO is important during Hold Over and that is why it is >> there. The changes are the DAC which is updated once a second. Very >> temperature sensitive. Cheap. We have done the tests 10811, OSA 8600, FRK >> and M100. For fun did use a cheap small OCXO, no performance change. Was >> done in Juerg's temperature stable basement. See attached picture. >> >>Bert Kehren >> My experiences with the T'Bolt have not been entirely satisfactory. If I >> set the loop >> lime constant long enough to get a satisfying smoothing of the GPS noise (a >> few hundred >> seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its >> ugly head and >> I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly has >> a double- >> oven XO, so I'd like to give that a try. But my wallet says "whoa"! >> >> According to Bodnar, his units do have some choices in the time constant >> setting. >> I've been considering ordering a Bodnar just for frequency agility, but >> have been >> holding off out of concern for the complications of dealing with a foreign >> supplier. >> >> Dana >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >> an email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Tbolt
One more comment on the Vectron OCXO. My Tbolt shows a tuning voltage of +0.4 Volt and has 3.6 Hz per Volt. Assuming the OCXO was sold to Trimble with 0 V and my unit has at least 12 years on it (4380 days) aging is 3.29 E-11 per day. Not bad for an OCXO. Bert Kehren ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Thunderbolts
I'll second the PRS-10, I have a used unit that I am very happy with. My only complaint is that a few times an hour it fails to produce a PPS. On my unit I expect that the problem is that it is going out of lock (used!!!). --mike On Wed, Jul 21, 2021 at 4:04 AM Dana Whitlow wrote: > Bert, remember that I need a very long locking loop time constant setting > in > order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a > holdover state anyway, all the time. > > Probably the smartest thing for me to do is to buy a spanking new PRS-10, > with the PPS locking feature present. Then I could just leave it locked to > GPS most all the time, but disconnect the PPS and let it go into holdover > on the rare occasions when I need a few hours of even better stability. > > Dana > > > On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts > > wrote: > > > There is a lot of misinformation out there. It is not the OCXO that > > changes, Bruce did extensive testing and I did some too. The Vectron is > > super, would like to know what is in it but do not want to open one. Once > > warmed up the stable OCXO temperature is a main contributor to the board > > temperature. Using a Dual Oven may give you a warm feeling but only adds > 1 > > more Watt of stable heat to the board making the temperature change > > smaller. The OCXO is important during Hold Over and that is why it is > > there. The changes are the DAC which is updated once a second. Very > > temperature sensitive. Cheap. We have done the tests 10811, OSA 8600, > FRK > > and M100. For fun did use a cheap small OCXO, no performance change. Was > > done in Juerg's temperature stable basement. See attached picture. > > > > Bert Kehren > > My experiences with the T'Bolt have not been entirely satisfactory. If I > > set the loop > > lime constant long enough to get a satisfying smoothing of the GPS noise > (a > > few hundred > > seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears > its > > ugly head and > > I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly > has > > a double- > > oven XO, so I'd like to give that a try. But my wallet says "whoa"! > > > > According to Bodnar, his units do have some choices in the time constant > > setting. > > I've been considering ordering a Bodnar just for frequency agility, but > > have been > > holding off out of concern for the complications of dealing with a > foreign > > supplier. > > > > Dana > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send > > an email to time-nuts-le...@lists.febo.com > > To unsubscribe, go to and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
