Re: [time-nuts] Maser 0.7 nsec jumps solved
Hold your horses folks. There is more on this tale! To recap we put the SSR on the aircon (at zero crossing) and the jumps got very very worse. So we turned the aircon off again (winter here - so not really needed) and the jumps dropped, but didn't go away. :-( So we also have a heater in the room (simple 1200W column heater) and a temperature monitor that turns the cooling or heating on as appropriate. So we also replaced the heating relay with an SSR and it all now seems to have gone away. We are now thinking that the aircon AND heating *relays* had started to pit after years of use and so give off radio transients which managed to get in and interfere with the extremely low (-100 dBm) signal coming from the physics package and going into the maser electronics. We have now run for four days with no clock jumps with both aircon and heater on and with 0V crossing SSR relays. "Welcome to the jungle, we've got fun and games..." Jim Palfreyman On 3 June 2016 at 15:00, Jim Palfreymanwrote: > Hi All, > > Thanks so much for your input and thoughts. It has really proved helpful > here at the observatory. > > As it turned out we easily obtained a zero-crossing solid state relay so > we thought we'd try it. > > And, drumroll.. > > > > It made things so much terribly *worse* than ever before. (As predicted by > many of you above.) > > We are going to try a SSR that switches at the peak - but we need to order > one. So stay tuned on those results. > > There is of course the "move the bloody thing far away from the maser" > solution which could end up being a serious option. These air conditioning > units are small and cheap (window-type), so we are trying to find the > cheapest solution - and if that ends up being some ducting - so be it! > > > Jim Palfreyman > > > > On 26 May 2016 at 13:13, Andy wrote: > >> On Wed, May 25, 2016 at 12:59 PM, Mike Monett < >> timen...@binsamp.e4ward.com> >> wrote: >> >> LTspice shows switching at 0V is the best point in time. ... >> >> >> >> Bzzzt! Your simulation is seriously flawed, and your conclusions are >> wrong. What you forgot, or may not have realized, is that SPICE's initial >> transient solution is obtained by having the signal sources already turned >> on (at the moment of the Big Bang) and set to their initial value, so the >> current through L2 is limited by DC conditions. That is not anything >> close >> to switching the driving voltages on. It is having one waveform sit at >> +169.7V DC for a very long time ('forever'), and then letting it follow a >> cosine wave. >> >> Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms >> uic) and see what it shows. Using UIC forces the initial voltage to be 0V >> at time=0, the start of the simulation. That's like having the switch >> initially open. >> >> Or if you don't like that, multiply the sources by a PWL waveform that >> starts both voltages at 0V and then switches them on, a few milliseconds >> into the simulation, with the appropriate phase. >> >> Or use an actual switch. LTspice has a switch element you could use. >> >> I guarantee you, the case with the voltage switching on at the 0V point in >> the voltage waveform, causes greater currents. >> >> The smaller surge current happens when the source is connected at the >> moment when the current i(t) would be 0A if it were a continuous waveform. >> For an inductive load, this happens when the voltage v(t) would be +/- >> peak >> (or near peak, for a real load which has both inductance and a little >> resistance). This condition also results in no surge, thus no L/R decay. >> >> All of this might not be relevant to a mechanical system, where surge >> current is caused by rotational inertia, rather than anything electrical. >> >> Regards, >> Andy >> ___ >> 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] Maser 0.7 nsec jumps solved
To All; I found a significant error in the LTspice analysis. I was wondering how the current could jump instantaneously at zero when the voltage is applied at the peak. That violates magnetism. It turns out it doesn't. When LTspice starts an analysis, it first calculates the operating point. For the Sine voltage source at 90 degrees, it applies the full voltage across the load. In this case, it was 169.7V across 1 ohm, resulting in 169.7 Amps. That is what was plotted, and is a significant error. I embarked on a search to find examples where switching at the peak could reduce the inrush current. Out of 13 examples I analyzed, I found only one that involves unloaded transformers. I found many references that discuss transformer inrush current caused by core saturation. This is a serious problem as it puts stress on the components and reduces operating life. I could find no reference that states switching at the peak would reduce or eliminate the inrush current. I also found most major suppliers do not offer SSR's that will switch at the peak. Obviously, switching at the peak would be worse for capacitive loads. This was a major project and turned out to take a lot more time and effort than expected. For those who may be interested, the results are shown at http://www.pst.netii.net/timenuts/zvs.htm MRM ___ 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] Maser 0.7 nsec jumps solved
Jim, My head is precisely in the get it away from the unit approach. Did not mention it for the following reason. Its well understood and for time-nut boring. Its more fun to figure out peak currents and such. But I tend to fall into the get it done camp and move on. That doesn't mean its a simple answer. Flex duct is bad. So only use it in the last few feet. You want low resistance hard duct. Then the fun of the return feed. Often overlooked and poorly considered. Regards Paul WB8TSL On Fri, Jun 3, 2016 at 1:00 AM, Jim Palfreymanwrote: > Hi All, > > Thanks so much for your input and thoughts. It has really proved helpful > here at the observatory. > > As it turned out we easily obtained a zero-crossing solid state relay so we > thought we'd try it. > > And, drumroll.. > > > > It made things so much terribly *worse* than ever before. (As predicted by > many of you above.) > > We are going to try a SSR that switches at the peak - but we need to order > one. So stay tuned on those results. > > There is of course the "move the bloody thing far away from the maser" > solution which could end up being a serious option. These air conditioning > units are small and cheap (window-type), so we are trying to find the > cheapest solution - and if that ends up being some ducting - so be it! > > > Jim Palfreyman > > > > On 26 May 2016 at 13:13, Andy wrote: > > > On Wed, May 25, 2016 at 12:59 PM, Mike Monett < > timen...@binsamp.e4ward.com > > > > > wrote: > > > > LTspice shows switching at 0V is the best point in time. ... > > > > > > > > Bzzzt! Your simulation is seriously flawed, and your conclusions are > > wrong. What you forgot, or may not have realized, is that SPICE's > initial > > transient solution is obtained by having the signal sources already > turned > > on (at the moment of the Big Bang) and set to their initial value, so the > > current through L2 is limited by DC conditions. That is not anything > close > > to switching the driving voltages on. It is having one waveform sit at > > +169.7V DC for a very long time ('forever'), and then letting it follow a > > cosine wave. > > > > Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms > > uic) and see what it shows. Using UIC forces the initial voltage to be > 0V > > at time=0, the start of the simulation. That's like having the switch > > initially open. > > > > Or if you don't like that, multiply the sources by a PWL waveform that > > starts both voltages at 0V and then switches them on, a few milliseconds > > into the simulation, with the appropriate phase. > > > > Or use an actual switch. LTspice has a switch element you could use. > > > > I guarantee you, the case with the voltage switching on at the 0V point > in > > the voltage waveform, causes greater currents. > > > > The smaller surge current happens when the source is connected at the > > moment when the current i(t) would be 0A if it were a continuous > waveform. > > For an inductive load, this happens when the voltage v(t) would be +/- > peak > > (or near peak, for a real load which has both inductance and a little > > resistance). This condition also results in no surge, thus no L/R decay. > > > > All of this might not be relevant to a mechanical system, where surge > > current is caused by rotational inertia, rather than anything electrical. > > > > Regards, > > Andy > > ___ > > 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] Maser 0.7 nsec jumps solved
Hi All, Thanks so much for your input and thoughts. It has really proved helpful here at the observatory. As it turned out we easily obtained a zero-crossing solid state relay so we thought we'd try it. And, drumroll.. It made things so much terribly *worse* than ever before. (As predicted by many of you above.) We are going to try a SSR that switches at the peak - but we need to order one. So stay tuned on those results. There is of course the "move the bloody thing far away from the maser" solution which could end up being a serious option. These air conditioning units are small and cheap (window-type), so we are trying to find the cheapest solution - and if that ends up being some ducting - so be it! Jim Palfreyman On 26 May 2016 at 13:13, Andywrote: > On Wed, May 25, 2016 at 12:59 PM, Mike Monett > > wrote: > > LTspice shows switching at 0V is the best point in time. ... > > > > Bzzzt! Your simulation is seriously flawed, and your conclusions are > wrong. What you forgot, or may not have realized, is that SPICE's initial > transient solution is obtained by having the signal sources already turned > on (at the moment of the Big Bang) and set to their initial value, so the > current through L2 is limited by DC conditions. That is not anything close > to switching the driving voltages on. It is having one waveform sit at > +169.7V DC for a very long time ('forever'), and then letting it follow a > cosine wave. > > Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms > uic) and see what it shows. Using UIC forces the initial voltage to be 0V > at time=0, the start of the simulation. That's like having the switch > initially open. > > Or if you don't like that, multiply the sources by a PWL waveform that > starts both voltages at 0V and then switches them on, a few milliseconds > into the simulation, with the appropriate phase. > > Or use an actual switch. LTspice has a switch element you could use. > > I guarantee you, the case with the voltage switching on at the 0V point in > the voltage waveform, causes greater currents. > > The smaller surge current happens when the source is connected at the > moment when the current i(t) would be 0A if it were a continuous waveform. > For an inductive load, this happens when the voltage v(t) would be +/- peak > (or near peak, for a real load which has both inductance and a little > resistance). This condition also results in no surge, thus no L/R decay. > > All of this might not be relevant to a mechanical system, where surge > current is caused by rotational inertia, rather than anything electrical. > > Regards, > Andy > ___ > 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] Maser 0.7 nsec jumps solved
On Wed, May 25, 2016 at 12:59 PM, Mike Monettwrote: LTspice shows switching at 0V is the best point in time. ... Bzzzt! Your simulation is seriously flawed, and your conclusions are wrong. What you forgot, or may not have realized, is that SPICE's initial transient solution is obtained by having the signal sources already turned on (at the moment of the Big Bang) and set to their initial value, so the current through L2 is limited by DC conditions. That is not anything close to switching the driving voltages on. It is having one waveform sit at +169.7V DC for a very long time ('forever'), and then letting it follow a cosine wave. Re-run the simulation with "UIC" added to the .tran statement (.tran 50ms uic) and see what it shows. Using UIC forces the initial voltage to be 0V at time=0, the start of the simulation. That's like having the switch initially open. Or if you don't like that, multiply the sources by a PWL waveform that starts both voltages at 0V and then switches them on, a few milliseconds into the simulation, with the appropriate phase. Or use an actual switch. LTspice has a switch element you could use. I guarantee you, the case with the voltage switching on at the 0V point in the voltage waveform, causes greater currents. The smaller surge current happens when the source is connected at the moment when the current i(t) would be 0A if it were a continuous waveform. For an inductive load, this happens when the voltage v(t) would be +/- peak (or near peak, for a real load which has both inductance and a little resistance). This condition also results in no surge, thus no L/R decay. All of this might not be relevant to a mechanical system, where surge current is caused by rotational inertia, rather than anything electrical. Regards, Andy ___ 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] Maser 0.7 nsec jumps solved
Am 25.05.2016 um 18:59 schrieb Mike Monett: This analysis shows switching at 0V is the best option. No, it doesn't. :-) First, the single inductor does not represent a transformer; the second inductor and the coupling declaration ( style: K1 L1 L2 0.99 or so) and the load are missing. The most important thing is that the Inductor is nonlinear which is not represented in the model. If there has remained some magnetism in the core from previous operation, the transformer won't be able to further increase the magnetism as needed to induce an opposing voltage in the primary winding. When the core saturates, the inductance collapses and leaves only the copper resistance to limit the current. The catastrophe builds up in the first 90 degrees of the source wave, not right at the start. In the simulation, the current at t=0 is at its maximum already when at t=0 the input voltage is just switched on. You'd expect that from a capacitor, never from an inductor. The reason is that the simulation does not really start at t=0, but much earlier. The simulator computes the conductance matrix, applies the initial sources and waits until everything has calmed down. That may require repeated recalculation of the matrix to respect nonlinearities. Your circuit must contain hidden resistors btw, otherwise the computation of the initial condition at "t<=0" would result in numeric overflow as required by an assumed initial DC voltage across an inductor, before the transient simulation. One can enforce initial conditions with statements like .IC v(my_node) = 0V regards, Gerhard BTW I've got the first 20 pcs. of the VCXO carrier / voltage regulator / lock to reference / squarer / iso amp or frequency doubler / 1pps board. That won't be soldering for beginners or jittery hands. :-) ___ 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] Maser 0.7 nsec jumps solved
On Wed, May 25, 2016 at 9:59 AM, Mike Monettwrote: > >Am 23.05.2016 um 05:15 schrieb Jim Palfreyman: > >> As far as a remedy goes we are going to try a solid state relay that > only > >> switches on at 0V in the AC waveform. This should slow the inrush > current, > >> and hopefully the magnetic impulse. > > > >In the context of transformers and motors, switching on at 0V is > >actually the worst point in time. > > > >< https://de.wikipedia.org/wiki/Einschalten_des_Transformators > (German) > > > >< > > > http://electrical-engineering-portal.com/practical-considerations-of-transformer-inrush-current > > > > > > >regards, Gerhard > > LTspice shows switching at 0V is the best point in time. With no > flux in the magnetics, the inrush current is limited by the circuit > resistance. The magnitude is given by Ohm's law: I = E / R. > > Switching at 0V, > > I = E / R > = 0 / R > = 0A > > However, switching at the peak of the voltage can give very high > inrush currents. You can verify this with LTspice. The schematic is > at > > http://www.pst.netii.net/misc/48b961a6.gif > > There are two circuits. They are identical except the second has the > applied voltage shifted by 90 degrees. The inductors have 1 Ohm > series resistance (not shown.) > > The waveforms are at > > http://www.pst.netii.net/misc/48b96217.gif > > The currents are IL1 and IL2. > > Switching at 0V, IL1 starts at zero. It rises to a peak of 900mA, > then falls back to zero. The DC offset takes 3 or 4 seconds to > decay, then the current is stable at zero +/- 450mA. > > Switching at the peak, IL2 is > > I = E / R > = 169.7 / 1 > = 169.7A > Er, no. It's an RL circuit for which: V(R) = E(1-e^(-(R/L)t) so I(R) = I(L) = (E/R)(1-e^(-(R/L)t) for t close to zero where E is essentially constant, I is going to rise with the time constant of R/L which for a 1H inductor and 1 ohm resistance is 1 second. I suggest running the simulation with a pulse voltage source, Tdelay 1ms, period 1s, Ton 0.5s (Period and Ton are fairly arbitrary, the Tdelay is important). You only need to run the simulation for a few ms. You will get a very different result. Now as Poul-Henning Kamp suggested, an induction motor is anything but an ideal inductor... ___ 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] Maser 0.7 nsec jumps solved
In message, "Mike Monett" writes: >The wikipedia article states "To avoid magnetic inrush, only for >transformers with an air gap in the core, the inductive load needs >to be synchronously connected near a supply voltage peak." You ought to have stopped and wondered at the "with an air gap in the core" and pondered if you SPICE models use of an ideal inductor was appropriate for something as electrically complex as an induction motor... -- 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] Maser 0.7 nsec jumps solved
>Am 23.05.2016 um 05:15 schrieb Jim Palfreyman: >> As far as a remedy goes we are going to try a solid state relay that only >> switches on at 0V in the AC waveform. This should slow the inrush current, >> and hopefully the magnetic impulse. > >In the context of transformers and motors, switching on at 0V is >actually the worst point in time. > >< https://de.wikipedia.org/wiki/Einschalten_des_Transformators > (German) > >< >http://electrical-engineering-portal.com/practical-considerations-of-transformer-inrush-current > > > >regards, Gerhard LTspice shows switching at 0V is the best point in time. With no flux in the magnetics, the inrush current is limited by the circuit resistance. The magnitude is given by Ohm's law: I = E / R. Switching at 0V, I = E / R = 0 / R = 0A However, switching at the peak of the voltage can give very high inrush currents. You can verify this with LTspice. The schematic is at http://www.pst.netii.net/misc/48b961a6.gif There are two circuits. They are identical except the second has the applied voltage shifted by 90 degrees. The inductors have 1 Ohm series resistance (not shown.) The waveforms are at http://www.pst.netii.net/misc/48b96217.gif The currents are IL1 and IL2. Switching at 0V, IL1 starts at zero. It rises to a peak of 900mA, then falls back to zero. The DC offset takes 3 or 4 seconds to decay, then the current is stable at zero +/- 450mA. Switching at the peak, IL2 is I = E / R = 169.7 / 1 = 169.7A It takes over twice as long for the starting surge to decay. I could still detect it past 8 seconds. This analysis shows switching at 0V is the best option. If you wish to do further analysis, the LTspice .ASC and .PLT files are at http://www.pst.netii.net/misc/48b96262.zip The wikipedia article states "To avoid magnetic inrush, only for transformers with an air gap in the core, the inductive load needs to be synchronously connected near a supply voltage peak." https://en.wikipedia.org/wiki/Inrush_current Clearly, from the above LTspice waveforms, switching at the peak gives the highest inrush surge that is possible to obtain. It also takes the longest time to decay. MRM ___ 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] Maser 0.7 nsec jumps solved
In message <57441aca.8070...@arcor.de>, Gerhard Hoffmann writes: >Am 23.05.2016 um 05:15 schrieb Jim Palfreyman: >> As far as a remedy goes we are going to try a solid state relay that only >> switches on at 0V in the AC waveform. This should slow the inrush current, >> and hopefully the magnetic impulse. >> >> >In the context of transformers and motors, switching on at 0V is >actually the worst point in time. Well... The motor is almost certainly an "Squirrel-cage" induction motor and that means it is three phase, although one of the phases is probably created with a "starting capacitor". So which of the three phases is going to be the lucky one that switches at maximum voltage, or are you going to switch the phases on sequentially ? A 4kW Variable Frequency Drive costs less than $1k and allows you to control *both* the voltage/time and the frequency/time *both* during startup and during rundown. I wouldn't bother fuzzing around with hacks - I'd just go for the known-to-work solution. -- 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] Maser 0.7 nsec jumps solved
Am 23.05.2016 um 05:15 schrieb Jim Palfreyman: As far as a remedy goes we are going to try a solid state relay that only switches on at 0V in the AC waveform. This should slow the inrush current, and hopefully the magnetic impulse. In the context of transformers and motors, switching on at 0V is actually the worst point in time. < https://de.wikipedia.org/wiki/Einschalten_des_Transformators > (German) < http://electrical-engineering-portal.com/practical-considerations-of-transformer-inrush-current > regards, Gerhard ___ 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] Maser 0.7 nsec jumps solved
I like to disagree. In the late 90's I started to work on high efficiency boat air conditioners for my boat, written up in Power and Motor Yacht "COOL" January 2003. To reduce inverter load and eliminate the power of the relays I went to zero crossing opto couplers and triacs. Used it also on home AC systems in some places eliminating lamp flicker on poorly supplied homes. In a message dated 5/23/2016 11:11:08 P.M. Eastern Daylight Time, ai.egrps...@gmail.com writes: On Sun, May 22, 2016 at 11:15 PM, Jim Palfreymanwrote: As far as a remedy goes we are going to try a solid state relay that only > switches on at 0V in the AC waveform. This should slow the inrush current, > and hopefully the magnetic impulse. > If the load being switched on is inductive, it would be better to switch the AC waveform at the voltage peaks, not at 0V. This might seem counter-intuitive, but it's real. Switching on at the 0V crossing may maximize the current pulse through the magnetics. OTOH, if the origin of the impulse is mechanical in nature, neither remedy may help. Regards, Andy ___ 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] Maser 0.7 nsec jumps solved
On Sun, May 22, 2016 at 11:15 PM, Jim Palfreymanwrote: As far as a remedy goes we are going to try a solid state relay that only > switches on at 0V in the AC waveform. This should slow the inrush current, > and hopefully the magnetic impulse. > If the load being switched on is inductive, it would be better to switch the AC waveform at the voltage peaks, not at 0V. This might seem counter-intuitive, but it's real. Switching on at the 0V crossing may maximize the current pulse through the magnetics. OTOH, if the origin of the impulse is mechanical in nature, neither remedy may help. Regards, Andy ___ 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] Maser 0.7 nsec jumps solved
In message, Jim Palfr eyman writes: >As far as a remedy goes we are going to try a solid state relay that only >switches on at 0V in the AC waveform. This should slow the inrush current, >and hopefully the magnetic impulse. If that is not enough, consider a small VFD drive, and ramp up voltage+frequency over 10 seconds. It's slightly more intrusive, as you will need to remove the starting capacitor from the motor to install the VFD. -- 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] Maser 0.7 nsec jumps solved
As far as a remedy goes we are going to try a solid state relay that only switches on at 0V in the AC waveform. This should slow the inrush current, and hopefully the magnetic impulse. If this doesn't work, then a better model of air conditioner might have to be installed. These ones do come on with a big "thump". Jim Palfreyman On 22 May 2016 at 21:43, Magnus Danielsonwrote: > Jim, > > On 05/22/2016 03:58 AM, Jim Palfreyman wrote: > >> Hi all, >> >> Awhile back I posted about some mysterious 0.7 ns jumps in three different >> masers (of the same brand) at three different locations around Australia. >> >> Well we think we've found the problem. All three locations also have >> in-room air conditioners of the same brand. These are used for cooling >> only. When these units turn on, we think they induce a magnetic field from >> the inrush current that briefly disrupts the maser. We don't think it's >> electrical because moving to another phase did not change things. >> >> These air conditioners are all quite close to the masers. Typically a >> metre >> or 2 away. >> >> Much was done to discover this, but the clincher was that when the weather >> cooled enough at the southern most location (Hobart), we turned off the >> air >> con (only heating was needed) and the problem vanished. >> >> So there's a lesson here for all maser owners. The jump of 0.7 nsec is not >> much, but it's huge for VLBI and for time-nuts. >> > > Good that you have found the offender, but have you been able to remedy it > by other means than turning the AC off? > I think others H-maser owners would love to know, and potentially the > vendor you have. > > Cheers, > Magnus > ___ > 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] Maser 0.7 nsec jumps solved
Interesting math: Hydrogen maser frequency standards use the 1420 MHz line. Period of 1420MHz is 0.7 ns. It's not so clear to me that the maser itself is being disrupted, it seems more likely the external noise is inducing an extra count or causing a count to be slipped. A different Australian observatory 1400 MHz RFI problem: http://arxiv.org/abs/1504.02165 "Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explain all of the observed properties of the peryton signals." Tim N3QE On Sun, May 22, 2016 at 7:43 AM, Magnus Danielson < mag...@rubidium.dyndns.org> wrote: > Jim, > > On 05/22/2016 03:58 AM, Jim Palfreyman wrote: > >> Hi all, >> >> Awhile back I posted about some mysterious 0.7 ns jumps in three different >> masers (of the same brand) at three different locations around Australia. >> >> Well we think we've found the problem. All three locations also have >> in-room air conditioners of the same brand. These are used for cooling >> only. When these units turn on, we think they induce a magnetic field from >> the inrush current that briefly disrupts the maser. We don't think it's >> electrical because moving to another phase did not change things. >> >> These air conditioners are all quite close to the masers. Typically a >> metre >> or 2 away. >> >> Much was done to discover this, but the clincher was that when the weather >> cooled enough at the southern most location (Hobart), we turned off the >> air >> con (only heating was needed) and the problem vanished. >> >> So there's a lesson here for all maser owners. The jump of 0.7 nsec is not >> much, but it's huge for VLBI and for time-nuts. >> > > Good that you have found the offender, but have you been able to remedy it > by other means than turning the AC off? > I think others H-maser owners would love to know, and potentially the > vendor you have. > > Cheers, > Magnus > ___ > 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] Maser 0.7 nsec jumps solved
Hi Jim, Thanks much for the update. I can see how this was a pain to track down. For those that don't remember the issue, the archive starts here: https://www.febo.com/pipermail/time-nuts/2015-December/094904.html And note that 1 / 0.704 ns = 1420 MHz, the frequency of a H-maser. So it's either electrical or magnetic or seismic, yes? Does it happen every time the HVAC turns on/off? Can you run a high-resolution phase comparator during the event to find the time constant of the phase jump / cycle slip? 1 kHz sample rate should be more than enough. That may help narrow down which circuit is at fault. /tvb - Original Message - From: "Jim Palfreyman"To: "Discussion of precise time and frequency measurement" Sent: Saturday, May 21, 2016 6:58 PM Subject: [time-nuts] Maser 0.7 nsec jumps solved > Hi all, > > Awhile back I posted about some mysterious 0.7 ns jumps in three different > masers (of the same brand) at three different locations around Australia. > > Well we think we've found the problem. All three locations also have > in-room air conditioners of the same brand. These are used for cooling > only. When these units turn on, we think they induce a magnetic field from > the inrush current that briefly disrupts the maser. We don't think it's > electrical because moving to another phase did not change things. > > These air conditioners are all quite close to the masers. Typically a metre > or 2 away. > > Much was done to discover this, but the clincher was that when the weather > cooled enough at the southern most location (Hobart), we turned off the air > con (only heating was needed) and the problem vanished. > > So there's a lesson here for all maser owners. The jump of 0.7 nsec is not > much, but it's huge for VLBI and for time-nuts. > > > Jim Palfreyman > ___ > 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] Maser 0.7 nsec jumps solved
Hi That’s a pretty good example for the “why you don’t do your timescale based on a single brand of gear / single setup” file. Thanks for sharing!! Bob > On May 21, 2016, at 9:58 PM, Jim Palfreymanwrote: > > Hi all, > > Awhile back I posted about some mysterious 0.7 ns jumps in three different > masers (of the same brand) at three different locations around Australia. > > Well we think we've found the problem. All three locations also have > in-room air conditioners of the same brand. These are used for cooling > only. When these units turn on, we think they induce a magnetic field from > the inrush current that briefly disrupts the maser. We don't think it's > electrical because moving to another phase did not change things. > > These air conditioners are all quite close to the masers. Typically a metre > or 2 away. > > Much was done to discover this, but the clincher was that when the weather > cooled enough at the southern most location (Hobart), we turned off the air > con (only heating was needed) and the problem vanished. > > So there's a lesson here for all maser owners. The jump of 0.7 nsec is not > much, but it's huge for VLBI and for time-nuts. > > > Jim Palfreyman > ___ > 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] Maser 0.7 nsec jumps solved
Jim, On 05/22/2016 03:58 AM, Jim Palfreyman wrote: Hi all, Awhile back I posted about some mysterious 0.7 ns jumps in three different masers (of the same brand) at three different locations around Australia. Well we think we've found the problem. All three locations also have in-room air conditioners of the same brand. These are used for cooling only. When these units turn on, we think they induce a magnetic field from the inrush current that briefly disrupts the maser. We don't think it's electrical because moving to another phase did not change things. These air conditioners are all quite close to the masers. Typically a metre or 2 away. Much was done to discover this, but the clincher was that when the weather cooled enough at the southern most location (Hobart), we turned off the air con (only heating was needed) and the problem vanished. So there's a lesson here for all maser owners. The jump of 0.7 nsec is not much, but it's huge for VLBI and for time-nuts. Good that you have found the offender, but have you been able to remedy it by other means than turning the AC off? I think others H-maser owners would love to know, and potentially the vendor you have. Cheers, Magnus ___ 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.