Re: [time-nuts] Maser 0.7 nsec jumps solved

[Jim Palfreyman]

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 Palfreyman  wrote:

> 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.
>>
>
>
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Mike Monett]

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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[paul swed]

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 Palfreyman  wrote:

> 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.
> >
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Jim Palfreyman]

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  >
> 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
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>
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[time-nuts] Maser 0.7 nsec jumps solved

[al wolfe]

Maybe the simplest solution would be to try a rudimentary form of
step-start relay to crank the A/C compressor. This used to be quite
common before the days of VFD's and such.

The regular start relay applies power to the motor via a resistor that
limits inrush current to some safe level to start the motor turning.
When the motor reaches a certain speed the voltage across the resistor
drops enough that a relay down stream of the resistor picks up and
shorts out the resistor applying full voltage to the compressor.

This method was used in many motor circuits, several broadcast
transmitters, and some ham radio amplifiers. Some applications use a
timer to energize the second relay. And, of course, there needs to be
some precaution paid to deal with a locked rotor.

Al, aka k9si
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Andy]

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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Gerhard Hoffmann]

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.  :-)






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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Orin Eman]

On Wed, May 25, 2016 at 9:59 AM, Mike Monett 
wrote:

> >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...
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Poul-Henning Kamp]

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.
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Mike Monett]

>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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Poul-Henning Kamp]

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.
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Gerhard Hoffmann]

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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Bert Kehren via time-nuts]

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 Palfreyman  
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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Andy]

On Sun, May 22, 2016 at 11:15 PM, Jim Palfreyman  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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Poul-Henning Kamp]

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.
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[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.

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 
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
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Tim Shoppa]

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
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> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
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>
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Tom Van Baak]

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" <jim77...@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.
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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Bob Camp]

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  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.

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Re: [time-nuts] Maser 0.7 nsec jumps solved

[Magnus Danielson]

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
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[time-nuts] Maser 0.7 nsec jumps solved

[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
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