Empathy List Archives

JP

Jim Palfreyman

Sun, May 22, 2016 1:58 AM

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

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

MD

Magnus Danielson

Sun, May 22, 2016 11:43 AM

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

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

BC

Bob Camp

Sun, May 22, 2016 12:01 PM

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 Palfreyman jim77742@gmail.com 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.

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.

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 Palfreyman <jim77742@gmail.com> 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. > > > 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.

TV

Tom Van Baak

Sun, May 22, 2016 1:09 PM

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" jim77742@gmail.com
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
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.

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" <jim77742@gmail.com> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> 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.

TS

Tim Shoppa

Sun, May 22, 2016 2:44 PM

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 <
magnus@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.

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 < magnus@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. >

JP

Jim Palfreyman

Mon, May 23, 2016 3:15 AM

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 Danielson magnus@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.

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 Danielson <magnus@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. >

PK

Poul-Henning Kamp

Mon, May 23, 2016 6:44 AM

In message CALH-g5b0C+aBz53MUM7bkJ00441AvNxwFLc2RgjgPj=k1FPOKA@mail.gmail.com, 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
phk@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.

-------- In message <CALH-g5b0C+aBz53MUM7bkJ00441AvNxwFLc2RgjgPj=k1FPOKA@mail.gmail.com>, 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 phk@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.

A

Andy

Tue, May 24, 2016 2:24 AM

On Sun, May 22, 2016 at 11:15 PM, Jim Palfreyman jim77742@gmail.com wrote:

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

On Sun, May 22, 2016 at 11:15 PM, Jim Palfreyman <jim77742@gmail.com> wrote: 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

GH

Gerhard Hoffmann

Tue, May 24, 2016 9:11 AM

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

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

PK

Poul-Henning Kamp

Tue, May 24, 2016 10:55 AM

In message 57441ACA.8070609@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
phk@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.

-------- In message <57441ACA.8070609@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 phk@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@lists.febo.com

Maser 0.7 nsec jumps solved