Re: [time-nuts] backfill
Hi You do work pretty hard to turn the metal can into a getter. The other issue is that the adsorption and desorption rates are quite different. Once you get the “stuff” into a layer state, it takes a long time to get it back out. Much better to not have it there in the first place. If the precision crystal is being used in a TCXO, water has the nasty tendency to freeze. When it does, you get a frequency bump. That’s a difficult thing to compensate for. Does it occur at < -65 (you hope) or at -45 (you hope not) ? The practical approach is to get rid of as much of it as you possibly can. Bob > On Jun 10, 2017, at 12:22 AM, Neville Michiewrote: > > It is possible that the ageing of a crystal is associated with the > redistribution of the surface water > monolayer, under the influence of the minute temperature gradient of an > oscillating crystal. > Some energy is dissipated in the quartz, so some gradient may exist. > When a crystal is resting, the water may redistribute in the sealed package, > but when run again, the water > redistributes due to the temperature differences. > Adsorbed water is in equilibrium with its environment, and, given time, will > migrate along temperature gradients. > It could be just one more mechanism in frequency drift. > I would try using a reactive metal getter in the package to pick up any > mobile water molecules. > > cheers, > > Neville Michie > >> On 10 Jun 2017, at 9:52 AM, Bob kb8tq wrote: >> >> Hi >> >> You can’t quite process a crystal at 300C, but you can get close. >> >> Bob >> >>> On Jun 9, 2017, at 7:38 PM, Neville Michie wrote: >>> >>> My memory of high vacuum work is that you need to pump for 4 hours >>> at 300C to remove the water monolayer from glass. >>> On top of the that water monolayer is another water monolayer that comes >>> off more easily, >>> and on top of that another……….. >>> >>> cheers, >>> Neville Michie >>> >>> On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist wrote: On 6/8/2017 5:08 PM, Bob kb8tq wrote: > Hi > In this case hydrogen + oxygen (like from oxidized metal) goes to H20. > You very much do > not want water running around inside your crystal holder… Helium is inert. > Bob Exactly right Bob. The 10811 guys used to go nuts about keeping water out of their vacuum system. There were certain temperatures known as "water points" at which some water was released. The retained water was in spite of the temperature already being above 100 degrees C (boiling). It has something to do with monolayers of water molecules not boiling away. Rick N6RK ___ 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. >> >> ___ >> 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. ___ 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.
Re: [time-nuts] backfill
It is possible that the ageing of a crystal is associated with the redistribution of the surface water monolayer, under the influence of the minute temperature gradient of an oscillating crystal. Some energy is dissipated in the quartz, so some gradient may exist. When a crystal is resting, the water may redistribute in the sealed package, but when run again, the water redistributes due to the temperature differences. Adsorbed water is in equilibrium with its environment, and, given time, will migrate along temperature gradients. It could be just one more mechanism in frequency drift. I would try using a reactive metal getter in the package to pick up any mobile water molecules. cheers, Neville Michie > On 10 Jun 2017, at 9:52 AM, Bob kb8tqwrote: > > Hi > > You can’t quite process a crystal at 300C, but you can get close. > > Bob > >> On Jun 9, 2017, at 7:38 PM, Neville Michie wrote: >> >> My memory of high vacuum work is that you need to pump for 4 hours >> at 300C to remove the water monolayer from glass. >> On top of the that water monolayer is another water monolayer that comes off >> more easily, >> and on top of that another……….. >> >> cheers, >> Neville Michie >> >> >>> On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist >>> wrote: >>> >>> >>> >>> On 6/8/2017 5:08 PM, Bob kb8tq wrote: Hi In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do not want water running around inside your crystal holder… Helium is inert. Bob >>> >>> Exactly right Bob. The 10811 guys used to go nuts >>> about keeping water out of their vacuum system. >>> There were certain temperatures known as "water >>> points" at which some water was released. >>> The retained water was in spite of the temperature >>> already being above 100 degrees C (boiling). >>> It has something to do with monolayers of >>> water molecules not boiling away. >>> >>> Rick N6RK >>> ___ >>> 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. > > ___ > 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.
Re: [time-nuts] backfill
Hi Well one thing that happens is that the glue that holds the blank in the holder turns to ash …. Bob > On Jun 9, 2017, at 8:31 PM, Hal Murraywrote: > > >> You can’t quite process a crystal at 300C, but you can get close. > > What happens if you get it too hot or too long? What's the limiting factor? > > > -- > These are my opinions. I hate spam. > > > > ___ > 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.
Re: [time-nuts] backfill
alpha quartz to beta quartz phase transition at 573C amongst other factors. Bruce > > On 10 June 2017 at 12:31 Hal Murraywrote: > > > > > > You can’t quite process a crystal at 300C, but you can get close. > > > > > > What happens if you get it too hot or too long? What's the limiting > factor? > > -- > These are my opinions. I hate spam. > > ___ > 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.
Re: [time-nuts] backfill
> You canât quite process a crystal at 300C, but you can get close. What happens if you get it too hot or too long? What's the limiting factor? -- These are my opinions. I hate spam. ___ 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.
Re: [time-nuts] backfill
Hi You can’t quite process a crystal at 300C, but you can get close. Bob > On Jun 9, 2017, at 7:38 PM, Neville Michiewrote: > > My memory of high vacuum work is that you need to pump for 4 hours > at 300C to remove the water monolayer from glass. > On top of the that water monolayer is another water monolayer that comes off > more easily, > and on top of that another……….. > > cheers, > Neville Michie > > >> On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist >> wrote: >> >> >> >> On 6/8/2017 5:08 PM, Bob kb8tq wrote: >>> Hi >>> In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You >>> very much do >>> not want water running around inside your crystal holder… Helium is inert. >>> Bob >> >> Exactly right Bob. The 10811 guys used to go nuts >> about keeping water out of their vacuum system. >> There were certain temperatures known as "water >> points" at which some water was released. >> The retained water was in spite of the temperature >> already being above 100 degrees C (boiling). >> It has something to do with monolayers of >> water molecules not boiling away. >> >> Rick N6RK >> ___ >> 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. ___ 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.
Re: [time-nuts] backfill
My memory of high vacuum work is that you need to pump for 4 hours at 300C to remove the water monolayer from glass. On top of the that water monolayer is another water monolayer that comes off more easily, and on top of that another……….. cheers, Neville Michie > On 9 Jun 2017, at 10:57 AM, Richard (Rick) Karlquist> wrote: > > > > On 6/8/2017 5:08 PM, Bob kb8tq wrote: >> Hi >> In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You >> very much do >> not want water running around inside your crystal holder… Helium is inert. >> Bob > > Exactly right Bob. The 10811 guys used to go nuts > about keeping water out of their vacuum system. > There were certain temperatures known as "water > points" at which some water was released. > The retained water was in spite of the temperature > already being above 100 degrees C (boiling). > It has something to do with monolayers of > water molecules not boiling away. > > Rick N6RK > ___ > 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.
Re: [time-nuts] backfill
Poul-Henning wrote: Next down the line is hydrogen, which comes with a shitload of issues. No argument there. But other methods all have their own shitloads -- it just depends on which shitload the designers dislike the least. you will find little love for hydrogen cooling [today] In 1993 Siemens put the first 170MVA air-cooled generator optimized by computer simulations of the flow-fields and since then hydrogen cooling has been confined to an ever-decreasing top tier of name-plate power. Certainly there are other ways, and hydrogen cooling may have decreased in popularity in the decades since I was paying attention (I consulted for a turbine generator manufacturer in the late '80s). But there are lots of hydrogen-cooled alternators in service, and it appears that they are still being built. 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.
Re: [time-nuts] backfill
In message <593a4677.5080...@yandex.com>, Charles Steinmetz writes: >The insides of mains alternators are almost entirely metal -- tons and >tons of copper tubing, and the casings and rotor shaft are steel. And >the alternators must operate at a relative humidity of absolute zero. This is close to to being "not even wrong". There is no requirement for "a relative humidity of absolute zero", which is theoretically impossible if there is any iron around. There are however stringent requirements for non-corrosion, dielectric potential, cooling, corona behaviour etc. etc. Cooling the stator is a no-brainer, it is almost always water-cooled. If they could afford to use helium to cool the rotor, they would jump on it instantly, but the cost is prohibitive at their leakage rates. Pure water would also be workable, but its high density means it cannot be used to cool the rotor without a serious hit to efficiency. Next down the line is hydrogen, which comes with a shitload of issues. Apart from all the obvious issues, lube-oil degradation, polymer degradation, fire-risk, risk of explosion, health-risk etc. hydrogen has "interesting" solubility in metals. If you want to purify hydrogen, you press it trhough a filter consisting of a solid slab of palladium, and that takes a lot less pressure than you would expect. For iron in particular, hydrogen means embrittlement, so a major focus in rotor design is to keep the hydrogen away from the iron. If you Google "generator hydrogen seal" and and you will find little love for hydrogen cooling. In 1993 Siemens put the first 170MVA air-cooled generator optimized by computer simulations of the flow-fields and since then the hydrogen cooling has been confined to an ever-decreasing top tier of name-plate power. Today fan cooling will take you to approx 400MVA and pressured air cooling will take you to about 600MVA. Above that, you are, almost by definition, in a nuclear power plant, and all problems from hydrogen cooling of your single huge generator pale in comparison to having a handful of smaller generators in parallel. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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.
Re: [time-nuts] backfill
Hi Cold traps and vac-ion pumps were very common on precision crystal seal setups 50 years ago. They have gotten better since then…. Bob > On Jun 9, 2017, at 9:13 AM, jimluxwrote: > > On 6/8/17 1:19 PM, Bob kb8tq wrote: >> Hi >> >> If you look at the thermal conductivity vs very low pressures, the >> conductivity >> comes up pretty quickly from a hard vacuum. There is essentially no impact >> on Q. >> > > basically, when the mean free path gets to be shorter than the distance to > the wall, the thermal conductivity drops off. > > MFP = 65 nm at 1013 hPa = 760 torr > > So at 10-4 Pa/0.75E-3 micron (start of very high vacuum) the MFP is 65 cm > > High vacuum usually starts around 0.1 Pa (close to 1 micron), where the MFP > is 65 mm - this is where the MFP is comparable to the size of the stuff > you're pumping down, and where you can't use a "pump", but rather you need > something that flings the air molecules toward the exit (diffusion or turbo > molecular pump) or something that is like flypaper for molecules (sorption, > cold finger, etc.) > > > If you've got a "refrigeration" vacuum pump, they pull down to about 30-40 > microns - MFP is a few millimeters > > > > > > ___ > 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.
Re: [time-nuts] backfill
Hi My guess is that crystals are more sensitive to moisture than the alternators…. The level of “clean” you need in a precision crystal enclosure is way beyond what is required in a number of other areas. One layer of water molecules is way to much in a modern crystal. can and do use crystals as detectors of low levels of “stuff” for this very reason. Bob > On Jun 9, 2017, at 2:55 AM, Charles Steinmetzwrote: > > Bob wrote: > >> In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You >> very much do >> not want water running around inside your crystal holder… Helium is inert. > > The insides of mains alternators are almost entirely metal -- tons and tons > of copper tubing, and the casings and rotor shaft are steel. And the > alternators must operate at a relative humidity of absolute zero. The problem > is far from insurmountable, even at that huge scale. Dealing with it should > be very much easier at a scale of cubic centimeters. > > They use condensers to remove the water during the hydrogen purge cycle, > which (for mains alternators) lasts several weeks. I watched the procedure > several times 25 years ago, but I don't recall the particulars now. > > 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. ___ 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.
Re: [time-nuts] backfill
On 6/8/17 1:19 PM, Bob kb8tq wrote: Hi If you look at the thermal conductivity vs very low pressures, the conductivity comes up pretty quickly from a hard vacuum. There is essentially no impact on Q. basically, when the mean free path gets to be shorter than the distance to the wall, the thermal conductivity drops off. MFP = 65 nm at 1013 hPa = 760 torr So at 10-4 Pa/0.75E-3 micron (start of very high vacuum) the MFP is 65 cm High vacuum usually starts around 0.1 Pa (close to 1 micron), where the MFP is 65 mm - this is where the MFP is comparable to the size of the stuff you're pumping down, and where you can't use a "pump", but rather you need something that flings the air molecules toward the exit (diffusion or turbo molecular pump) or something that is like flypaper for molecules (sorption, cold finger, etc.) If you've got a "refrigeration" vacuum pump, they pull down to about 30-40 microns - MFP is a few millimeters ___ 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.
Re: [time-nuts] backfill (was: Poor man's oven)
The difficulty with hydrogen is to keep it where you want it. It does not take very much for it to leak out (or in, as the case may be) On Jun 8, 2017 4:58 PM, "Alan Melia" <alan.me...@btinternet.com> wrote: > Hi Bob, it also depends on what you allow to leak into the vacuum. > Hydrogen is a pretty effective remover of heat :-)) > Alan > G3NYK > > - Original Message - From: "Bob kb8tq" <kb...@n1k.org> > To: "Discussion of precise time and frequency measurement" < > time-nuts@febo.com> > Sent: Thursday, June 08, 2017 9:19 PM > Subject: Re: [time-nuts] backfill (was: Poor man's oven) > > > Hi >> >> If you look at the thermal conductivity vs very low pressures, the >> conductivity >> comes up pretty quickly from a hard vacuum. There is essentially no impact >> on Q. >> >> Bob >> >> On Jun 8, 2017, at 4:03 PM, Attila Kinali <att...@kinali.ch> wrote: >>> >>> On Thu, 8 Jun 2017 06:55:07 -0400 >>> Bob kb8tq <kb...@n1k.org> wrote: >>> >>> The simple answer is that the backfill is done because it does matter in >>>> a lot of >>>> cases. >>>> >>> >>> This raises the question, why there is backfill (just for thermal >>> conductivity?) >>> and how much it affects the Q of the crystal. >>> >>> Attila Kinali >>> >>> >>> -- >>> You know, the very powerful and the very stupid have one thing in common. >>> They don't alters their views to fit the facts, they alter the facts to >>> fit the views, which can be uncomfortable if you happen to be one of the >>> facts that needs altering. -- The Doctor >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>> ailman/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/m >> ailman/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/m > ailman/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.
Re: [time-nuts] backfill (was: Poor man's oven)
Wouldn't the low density of helium reduce some mechanical friction? I realize the motions are small but they are motions. The "Cousteau effect"? :) ___ 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.
Re: [time-nuts] backfill
Bob wrote: In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do not want water running around inside your crystal holder… Helium is inert. The insides of mains alternators are almost entirely metal -- tons and tons of copper tubing, and the casings and rotor shaft are steel. And the alternators must operate at a relative humidity of absolute zero. The problem is far from insurmountable, even at that huge scale. Dealing with it should be very much easier at a scale of cubic centimeters. They use condensers to remove the water during the hydrogen purge cycle, which (for mains alternators) lasts several weeks. I watched the procedure several times 25 years ago, but I don't recall the particulars now. 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.
Re: [time-nuts] backfill
Bob wrote: You really want to use Helium. Hydrogen is a bit reactive. I don't think it's a problem. The alternators on mains powerplants are filled with Hydrogen under fair pressure, and the internal materials and conditions are not that different from a crystal oscillator inside an oven. (IH was chosen both for its heat conduction and its low windage. Helium is enough worse on both counts that it was a non-starter. Of course, windage isn't important in a crystal oscillator.) In any case, it can't be any worse than filling space capsules with Oxygen 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.
Re: [time-nuts] backfill
On 6/8/2017 5:08 PM, Bob kb8tq wrote: Hi In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do not want water running around inside your crystal holder… Helium is inert. Bob Exactly right Bob. The 10811 guys used to go nuts about keeping water out of their vacuum system. There were certain temperatures known as "water points" at which some water was released. The retained water was in spite of the temperature already being above 100 degrees C (boiling). It has something to do with monolayers of water molecules not boiling away. Rick N6RK ___ 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.
Re: [time-nuts] backfill
Hi In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very much do not want water running around inside your crystal holder… Helium is inert. Bob > On Jun 8, 2017, at 7:18 PM, Charles Steinmetzwrote: > > Bob wrote: > >> You really want to use Helium. Hydrogen is a bit reactive. > > I don't think it's a problem. The alternators on mains powerplants are > filled with Hydrogen under fair pressure, and the internal materials and > conditions are not that different from a crystal oscillator inside an oven. > (IH was chosen both for its heat conduction and its low windage. Helium is > enough worse on both counts that it was a non-starter. Of course, windage > isn't important in a crystal oscillator.) > > In any case, it can't be any worse than filling space capsules with Oxygen > > 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. ___ 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.
Re: [time-nuts] backfill
Bob is exactly right. Read up on "mean free path" physics. Just a little air will take care of conduction. Full atmospheric pressure would drop the Q something like a factor of 2. In any event, conduction through the crystal mounts is plenty adequate for the tiny thermal mass of the crystal itself. The mounts are embedded in the ceramic header, which is fairly conductive. Rick N6RK On 6/8/2017 1:19 PM, Bob kb8tq wrote: Hi If you look at the thermal conductivity vs very low pressures, the conductivity comes up pretty quickly from a hard vacuum. There is essentially no impact on Q. Bob ___ 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.
Re: [time-nuts] backfill (was: Poor man's oven)
Hi You really want to use Helium. Hydrogen is a bit reactive. Bob > On Jun 8, 2017, at 5:49 PM, Alan Melia <alan.me...@btinternet.com> wrote: > > Hi Bob, it also depends on what you allow to leak into the vacuum. Hydrogen > is a pretty effective remover of heat :-)) > Alan > G3NYK > > - Original Message - From: "Bob kb8tq" <kb...@n1k.org> > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Sent: Thursday, June 08, 2017 9:19 PM > Subject: Re: [time-nuts] backfill (was: Poor man's oven) > > >> Hi >> >> If you look at the thermal conductivity vs very low pressures, the >> conductivity >> comes up pretty quickly from a hard vacuum. There is essentially no impact >> on Q. >> >> Bob >> >>> On Jun 8, 2017, at 4:03 PM, Attila Kinali <att...@kinali.ch> wrote: >>> >>> On Thu, 8 Jun 2017 06:55:07 -0400 >>> Bob kb8tq <kb...@n1k.org> wrote: >>> >>>> The simple answer is that the backfill is done because it does matter in a >>>> lot of >>>> cases. >>> >>> This raises the question, why there is backfill (just for thermal >>> conductivity?) >>> and how much it affects the Q of the crystal. >>> >>> Attila Kinali >>> >>> >>> -- >>> You know, the very powerful and the very stupid have one thing in common. >>> They don't alters their views to fit the facts, they alter the facts to >>> fit the views, which can be uncomfortable if you happen to be one of the >>> facts that needs altering. -- The Doctor >>> ___ >>> 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. > > ___ > 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.
Re: [time-nuts] backfill (was: Poor man's oven)
Hi Bob, it also depends on what you allow to leak into the vacuum. Hydrogen is a pretty effective remover of heat :-)) Alan G3NYK - Original Message - From: "Bob kb8tq" <kb...@n1k.org> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Thursday, June 08, 2017 9:19 PM Subject: Re: [time-nuts] backfill (was: Poor man's oven) Hi If you look at the thermal conductivity vs very low pressures, the conductivity comes up pretty quickly from a hard vacuum. There is essentially no impact on Q. Bob On Jun 8, 2017, at 4:03 PM, Attila Kinali <att...@kinali.ch> wrote: On Thu, 8 Jun 2017 06:55:07 -0400 Bob kb8tq <kb...@n1k.org> wrote: The simple answer is that the backfill is done because it does matter in a lot of cases. This raises the question, why there is backfill (just for thermal conductivity?) and how much it affects the Q of the crystal. Attila Kinali -- You know, the very powerful and the very stupid have one thing in common. They don't alters their views to fit the facts, they alter the facts to fit the views, which can be uncomfortable if you happen to be one of the facts that needs altering. -- The Doctor ___ 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. ___ 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.
Re: [time-nuts] backfill (was: Poor man's oven)
Hi If you look at the thermal conductivity vs very low pressures, the conductivity comes up pretty quickly from a hard vacuum. There is essentially no impact on Q. Bob > On Jun 8, 2017, at 4:03 PM, Attila Kinaliwrote: > > On Thu, 8 Jun 2017 06:55:07 -0400 > Bob kb8tq wrote: > >> The simple answer is that the backfill is done because it does matter in a >> lot of >> cases. > > This raises the question, why there is backfill (just for thermal > conductivity?) > and how much it affects the Q of the crystal. > > Attila Kinali > > > -- > You know, the very powerful and the very stupid have one thing in common. > They don't alters their views to fit the facts, they alter the facts to > fit the views, which can be uncomfortable if you happen to be one of the > facts that needs altering. -- The Doctor > ___ > 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.
[time-nuts] backfill (was: Poor man's oven)
On Thu, 8 Jun 2017 06:55:07 -0400 Bob kb8tqwrote: > The simple answer is that the backfill is done because it does matter in a > lot of > cases. This raises the question, why there is backfill (just for thermal conductivity?) and how much it affects the Q of the crystal. Attila Kinali -- You know, the very powerful and the very stupid have one thing in common. They don't alters their views to fit the facts, they alter the facts to fit the views, which can be uncomfortable if you happen to be one of the facts that needs altering. -- The Doctor ___ 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.