Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Peter Reilley]

Reading this paper makes one wonder if there are other improvements that
can be made to increase the robustness against jamming, software bugs, 
solar events

or hostile attacks to the GPS system

A suggestion:

Create a parallel terrestrial GPS system.   This would be a system of 
GPS transmitters
mounted on cell phone towers.   They would masquerade as GPS satellites 
(but unusually low
and stationary).   It would be ideal if they could have unique 
identifiers and be integrated
into the GPS receivers timing and location calculations as any other 
satellite.   If there
is no room in the existing ID space then the terrestrial node would take 
over the ID of
a satellite that is below the horizon.   When the satellite reappeared 
the terrestrial node

would simply take over a different below the horizon satellite's ID.

Such a system could be built out as needed.   It may not require any 
alterations to existing
GPS receivers.   It would not disrupt the operation of the existing 
satellite constellation.
It would protect against attacks on the satellite system by either a 
human enemy or a natural

one, the sun.

Each node need not contain an accurate time source like a cesium 
standard.   They could
derive timing from a neighbor.   Cesium reference nodes would be 
periodically placed around the
system.   Timing derivations would be more accurate since the distances 
would be much closer and

thereby encounter less environmental disturbance.

GPSDO units would prefer such close and stationary references vs distant 
moving ones.


Pete.

On 3/11/2018 5:26 PM, Magnus Danielson wrote:

Hi Andy,

On 03/11/2018 08:40 PM, Andy Backus wrote:

Thank you for your posting, Magnus.

Your information is very interesting.

Do you mind saying a little more about the "incident" on 26-JAN-2016?  I don't 
find reference to it in the link.  And my own TE plot for then shows no obvious 
disturbance.

Thanks.

Please read this:
https://rubidium.dyndns.org/~magnus/papers/GPSincidentA6.pdf

In short, the GPS to UTC time correction polynomial got screwed up.

I got email from NASA, ended up having to call NASA HQ and got invited
to Washington DC to present before the US PNT advisory board.

Among the stranger things I've done in my life, but it was fun.

Cheers,
Magnus
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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

Another purpose of the reheat process is to control moisture.   The term 
"moisture" here
describes the amount of liquid water in the steam as it flows through 
the system.   The spec

for this is generally about .25% moisture.

The temperature of the steam exiting the boiler is very close to the 
boiling point of water
at that pressure.   The energy to boil water is 970 BTU per lb. The 
energy to change
the temperature of water by 1 degree F is 1 BTU per lb.   Thus there is 
very little to be
gained by heating the steam hotter than it's boiling point.   You can't 
add that much
additional energy and have a temperature that you can handle.   Of 
course the boiling point

of water is quite high at these pressures.

The steam enters the turbine at very high temperature and pressure.   As 
it passes
through the many stages of the turbine you would like the pressure and 
temperature
of the steam to remain just above the boiling point.   You want to 
maintain that

balance of pressure and temperature to insure less than .25% moisture.

The reason that the steam must remain "just above" the boiling point is 
any condensation
produces liquid water.This liquid water is very destructive to the 
turbine blades.
The velocity of the steam in the turbine approaches supersonic speeds 
and any little
drops of water hitting the blades at those speeds erodes the steel.   
The areas of the
blades most at risk for this have a very hard material braised onto 
their surface.

But even this gets eroded.   I remember it being called "Stellite".

Reheat is used to raise the temperature of the steam to keep it above the
boiling point at certain stages in it's flow through the turbine.

There is a limit to how hot you can go.   Water has a critical point at 
705 degrees F
at 3200 PSI.Above this point there is no longer a sharp distinction 
between vapor
and water.   There have been super-critical power plants built. But when 
I was in
the business, in the 1970's, they were experimental and not reliable.   
I don't know

if that is true now.

Pete.

On 4/5/2017 5:44 PM, Bryan _ wrote:

There is a pretty nice "How it Works" video on steam turbines. As Pete mentions 
they use valving to control the speed of the turbines, interesting how they reheat the 
steam for the high/medium/low stages.


https://youtu.be/SPg7hOxFItI


-=Bryan=-



From: time-nuts <time-nuts-boun...@febo.com> on behalf of Peter Reilley 
<preilley_...@comcast.net>
Sent: April 5, 2017 9:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity

The response time in a large plant is very slow.   Large steam plants
running at steady
state are running with their steam valves wide open.   A partially
closed valve is an energy
loss and is only used when changes occur.

The power control for a plant running at a steady load is the amount of
fuel thrown into
the boiler.   When you want more power you shoot more gas, oil, or coal
into the boiler.
For a nuke you pull the control rods.   Behind all of this is a lot of
thermal mass.   Things
don't change quickly.

Pete.

On 4/5/2017 9:01 AM, jimlux wrote:

On 4/4/17 2:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is
kept stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

The line frequency is adjusted, for the most part, by adjusting the
prime power (steam valves, dam penstocks, etc.) on the generators at
power stations. That changes the speed, slightly, although as
generator 1 of N starts to get ahead, the electrical load increases,
and it slows down.

It's actually a pretty complex system, since there are a whole raft of
"spring constants" in between the multiple generators in a system,
there's phase shifts due to transmission line inductance and capacitance.

"Stabilizing" a system in the face of changing demand is a non-trivial
task.






Thomas D. Erb
t...@electrictime.com<mailto:t...@electrictime.com> /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com>>
[Facebook]<https://www.facebook.com/pages/Electric-Time-Company-Inc/127918073950854?ref=hl>[Twitter]<https://twitter.com/tower_clocks>[pinterest]<https://www.pinterest.com/electrictime/>

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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

The response time in a large plant is very slow.   Large steam plants 
running at steady
state are running with their steam valves wide open.   A partially 
closed valve is an energy

loss and is only used when changes occur.

The power control for a plant running at a steady load is the amount of 
fuel thrown into
the boiler.   When you want more power you shoot more gas, oil, or coal 
into the boiler.
For a nuke you pull the control rods.   Behind all of this is a lot of 
thermal mass.   Things

don't change quickly.

Pete.

On 4/5/2017 9:01 AM, jimlux wrote:

On 4/4/17 2:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is 
kept stable ?


Is the line frequency now directly tied to GPS clock - with no drift ?


The line frequency is adjusted, for the most part, by adjusting the 
prime power (steam valves, dam penstocks, etc.) on the generators at 
power stations. That changes the speed, slightly, although as 
generator 1 of N starts to get ahead, the electrical load increases, 
and it slows down.


It's actually a pretty complex system, since there are a whole raft of 
"spring constants" in between the multiple generators in a system, 
there's phase shifts due to transmission line inductance and capacitance.


"Stabilizing" a system in the face of changing demand is a non-trivial 
task.








Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest] 


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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

Think of it as an ocean liner trying to keep a dead straight course to 
it's destination.
It weighs many tons and wind and waves may drive it off it's path but 
the captain
can correct for this.   It eventually arrives at it's destination and is 
only a few feet

from the dock.

The total rotating mass of all the generators in a network is many times 
the mass of an
ocean liner.   The operators do their best to keep them running at the 
correct frequency.
Unexpected load changes can cause some divergence, but over time the 
average is

dead on.

When I installed power plants in the 1970's they has a special "clock" 
that showed the
cumulative error in terms of clock time.   The clock had two inputs, one 
from the utility
power and the other from some reference, possibly WWV.   Normally the 
"clock" was

pointing up at zero and not moving.

If the generator ran a little too fast the clock would move forward.   
As the operator
observed the clock moving away from zero he would reduce the plant's 
power and the
clock would move backward toward zero.   His goal was to keep the clock 
at zero and
not moving.   Thus, your bedside clock was always on time even if there 
were temporary

excursions fast or slow.

Pete.


On 4/4/2017 5:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is kept 
stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest]
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Re: [time-nuts] how many seconds out does GPS discipline being to improve Rubidium stability?

[Peter Reilley]

Could you do all three tests in parallel?   One unit under test driving 
three counters.
Each counter using a different reference signal, one on a OCXO, one on a 
rubidium,
and one on a GPS disciplined oscillator.   At each point in time during 
the test simply

choose the one that gives the best ADEV?

Pete.

On 2/11/2017 6:52 PM, Bob Camp wrote:

Hi

Using ADEV as an example (the other stuff will have it’s own curves, but the 
result is the same):

A typical Rb should have a stability at short tau that goes as 1/ square 
root(Tau). If you are at 2x10^-11 at 1 second, you
will be at 2x10^-12 at 100 seconds and 2x10^-13 at 1,000 seconds. Somewhere in 
the parts in 10^-13 that relation will
start to diverge from reality.

A fairly normal low frequency OCXO has a stability that is fairly flat with tau 
in the 1 to 100 second range. If they have been
on power constantly that “flat zone" may extend to 1,000 seconds. Floors should 
be in the low parts in 10^-12 to mid parts
in 10^-13 range.

A good OCXO *may* beat a normal Rb at 1,000 seconds. That may or may not be an 
issue in your case. It depends a lot
on what you are trying to do.

Simple solutions:

1) Run something better than an Rb. A hydrogen maser is one alternative (simple 
if you don’t have to pay for it).
2) Do all your measurements as three corner hats. You run two references and 
one DUT into gear that will do that sort of test.
3) Segment the measurements and use carefully selected references for those 
ranges.

None of those are actually simple. Number 3 sounds cool until you realize that 
you are switching test setups around a lot and
the devices you are using still need a setup like 2 to figure out which ones to 
use.

So do you need a GPS? What are the limits on your MTIE tests? (MTIE on an OCXO 
is highly dependent on several
things so there is no simple number there). A very normal quartz based GPSDO 
might be a fine reference for your test.

How much shorter are the other tests? Is ADEV at 1,000 seconds even of interest? 
If the answer is < 1,000 seconds a
Rb may not do you much good at all.

Lots of twists and turns.

Bob






On Feb 11, 2017, at 5:52 PM, gkk gb  wrote:

Thanks Bob,



I should clarify the MTIE measurement extends 10 seconds (the others are 
less time). Is it a reasonable question to ask if GPS is needed? Or are there 
other variables that are involved?



Good point about the temperature stability, I hadn't considered that. Can I 
place in a temperature chamber to provide a better thermal environment, or does 
that cause other issues (vibration from blowers, EMI noise, etc.)? Other ways 
to mitigate temperature changes?



It seems a Rubidium is good after a timescale of 100 s. What do people do below 100 s to 
characterize quartz oscillators. Do they simply try to find the most stable parts they 
can afford and break the x-axis (tau) into two regions using difference references for 
each? If so, are there generally accepted "gold" standards anyone can recommend 
for crystal products with the best stability to use as a reference between 0.1 and 100 
seconds, for example?



On February 11, 2017 at 6:29 AM Bob Camp  wrote:

Hi

Backing up a bit here.

On Feb 10, 2017, at 7:35 PM, gkk gb  wrote:

Hello experts, I need a Rubidium frequency reference for my company, and wonder 
if I also need to GPS discipline it.

I characterize crystal-based OCXOs for ADEV, MTIE, and TDEV, and my longest 
measurement time is 100,000 seconds (28 hours).

If your longest measurement is a 100,000 second ADEV, then your measurement 
time will be out in the
1,000,000 to 10,000,000 second range. Is that really what you are doing?

If 100,000 seconds ADEV is your longest measurement, what is the shortest tau 
you are interested in?
A Rb is not going to be much use for testing a good OCXO at shorter tau. Where 
the crossover happens
depends a lot on the grade of OCXO you are working with. By the time you get to 
1 second
most OCXO’s will be noticeably better than most Rb’s.

I'm looking at this graph from SRS for PRS10,

http://www.thinksrs.com/assets/instr/PRS10/PRS10diag2LG.gif

I would suggest that plot is probably not the best one to depend on for GPS 
performance. In a GPSDO setting
the cut over points are all over the place depending on which design you look 
at.

and thinking that as long as I calibrate a Rubidium source annually, there's no 
need for a GPS (since it only appears to degrade stability). Is this true in 
general, or is the graph misleading me because it may be true here, but not 
always.

The big issue is going to be temperature stability. If you have a Rb that is 
(say) 5x10^-10 over 0 to 50C, that is likely 1x10^-11 / C (or maybe more). A 2C 
delta in
your lab as the HVAC cycles will give you a 2x10^-11 “hump” in your ADEV plot.

Also consider that if you want an “easy” measurement of the devices you are 
testing, the reference source probably should be
5X 

Re: [time-nuts] Line Frequency standard change - Possible ?

[Peter Reilley]

They may well be willing to pay for more expensive equipment because they
can make money from it.   large industrial electricity users pay for the VAs
that they use.   Even though they are not energy the utility has to 
supply them.

The utility charges for this service.

If a solar farm also included a battery bank then they would be able to 
supply
VAs along with Watts just like a conventional generator.   With 
batteries solar

farms could contribute to grid stability just like other suppliers.

Pete.



On 2/10/2017 7:43 AM, David wrote:

On Thu, 09 Feb 2017 23:39:24 +, you wrote:


It is harder than it sounds.

Small solar inverters are the best, they an regulate down at milliseconds
notice, and many jurisdictions impose asymetric frequency bands on
them to exploit this.

Big inverters, no matter what you put behind them, get quite a bit
more expensive if they are designed to provide "non-VA" power,
because you suddenly have to run the current both ways in the same
half-cycle.

Nobody wants to pay for that voluntarily, and nobody are particular
keen to cause the first explosion/fire while they get the control-law
debugged.

Imagine how they will scream if they have to pay for fields of big
synchronous motors to be connected.

https://en.wikipedia.org/wiki/Synchronous_condenser
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Re: [time-nuts] Line Frequency standard change - Possible ?

[Peter Reilley]

Even in the old days a lot of devices were constant load, independent of 
voltage (within reason).
Anything regulated such as electric heat, electric hot water, and 
refrigerators are constant load.
Synchronous motors (most motors) are frequency dependent.   They do get 
less efficient at lower
voltages because their slip speed increases but that is a small percent 
of their running speed.
Non-synchronous motors are often speed regulated so they are constant 
load.   Electric transportation

is constant load.

I am sure that I could come up with more examples.

Utilities found that dropping the voltage was not very effective at 
shedding load in emergency

situations.   However, rolling blackouts do work very well.

Pete.

On 2/9/2017 6:55 PM, Poul-Henning Kamp wrote:


In message 

Re: [time-nuts] Line Frequency standard change - Possible ?

[Peter Reilley]

Isn't this "hard" lock to UTC creating a single point of failure? A 
solar burst, an EMP, or
a software error could leave us all in the dark.   After all, smart 
inverters could be
programmed to act like big lumps of rotating iron and be compatible with 
the current

system.

Pete.

On 2/9/2017 4:31 PM, Poul-Henning Kamp wrote:


In message <4fbdd81ddf04fc46870db1b9a747269202916...@mbx032-e1-va-8.exch032.ser
verpod.net>, "Thomas D. Erb" writes:


I was wondering if anyone was familiar with this proposal, is this
a uncoupling of line frequency from a time standard ?

The interesting thing about this is that all research and experiments
(for instance on the danish island Bornholm) indicates that the only
way we stand any chance of keeping future AC grids under control in the
medium term is to lock the frequency *hard* to UTC.

Its a very interesting topic.

In the traditional AC grid power is produced by big heavy lumps of
rotating iron.  This couples the grid frequency tightly to the
power-balance of the grid:  If the load increases, the generators
magnetic field drags harder slowing the rotor, lowering the frequency
and vice versa.

This makes the grid frequency a "proxy signal" for the power balance,
and very usefully so, because it travels well and noiselessly through
the entire AC grid.

The only other possible "balance signal" is the voltage, and it
suffers from a host of noise mechanisms, from bad contacts and
lightning strikes to temperature, but worst of all, it takes double
hit when you start big induction motors, thus oversignalling the
power deficit.

Where the frequency as "proxy" for grid balance reacts and can
be used to steering on a 100msec timescale, you need to average
a voltage "proxy" signal for upwards of 20 seconds to get the
noise down to level where you don't introduce instability.

The big picture problem is that we are rapidly retiring the rotating
iron, replacing it with switch-mode converters which do not "couple"
the frequency to power balance.

For instance HVDC/AC converters, solar panel farms, and increasingly
wind generators, do not try to drag down the frequency when they
cannot produce more or drag the frequency up when they can produce
more power, they just faithfully track whatever frequency all the
rotating lumps of iron have agreed on.

As more and more rotating iron gets retired, the grid frequency
eventually becomes useless as a "proxy-signal" for grid balance.

Informal and usually undocumented experiments have already shown
that areas of grids which previously were able to run in "island"
mode, are no longer able to do so, due to shortage of rotating iron.

One way we have found to make the voltage a usable fast-reacting
proxy for grid power-balance, is to lock the frequency to GNSS at
1e-5 s level at all major producers, which is trivial for all the
switch-mode kit, and incredibly hard and energy-inefficient for the
rotating iron producers.

The other way is to cut the big grids into smaller grids with HVDC
connections to decouple the frequencies, which allows us to relax
the frequency tolerance for each of these subgrids substantially.

This solution gets even better if you load the HVDC up with capacitance
to act as a short time buffers, but the consequences in terms of
short circuit energy are ... spectacular?

(It is already bad enough with cable capacitance in long HVDC
connections, do the math on 15nF/Km and 100.000 kV yourself.)

All these issues are compounded by the fact that the "50/60Hz or
bust" mentality has been tatooed on the nose of five generations
of HV engineers, to such an extent that many of them are totally
incapable of even imagining anything else, and they all just "know"
that DC is "impossible".

In the long term, HVDC is going to take over, because it beats HVAC
big time on long connections, and it is only a matter of getting
semiconductors into shape before that happens.  That however,
is by no means a trivial task:  It's all about silicon purity.




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Re: [time-nuts] What interrupts aging?

[Peter Reilley]

I am curious: is the quartz in a high quality quartz crystal perfect?
That is; is the


crystalline lattice perfect, without flaws or impurities?   I assume 
that the quartz is


grown in a furnace, can we grow perfect quartz crystals?

Pete.


On 2/5/2017 6:31 PM, Bob Camp wrote:

Hi

Aging can be caused by many things. Stress on the blank (and can and leads and 
plating and …) is one
source. There are good reasons to believe that quartz vs metal stress can take 
> 1 month to settle out
to the 90% level. Particle (think borders down to atoms) equilibrium inside the 
can is another source.
Adsorption / desorption rates on many of the likely candidates also run out into 
the > 1 month range.
More or less — you can adsorb stuff in a few seconds that takes many weeks to 
desorb. Yes this is
only the start of a very long list ….

How long an interruption to stir things up? Does the oven go to full power 
after your interruption? If it
does, things are likely to get tossed around and aging (or retrace or warmup or 
whatever you want to
call it) is going to get going.

Pile on top of this the fact that crystals are not the only thing that does 
aging like things. Capacitors
have a fun characteristic known as dielectric absorption. Some (tantalums) have 
leakage that drops
a LOT with time spent at temperature and voltage. Either way,  bump the voltage 
and things move around
for a while. Use the wrong caps and it can be quite a while.

Next layer is keeping the OCXO at the same temperature. When a “normal” OCXO is 
sitting there on
the bench, it’s in it’s own very specific temperate zone. Convection (and maybe 
other things) have acted
over quite a while to set up that zone. Touch it / bump it / move it / blow on 
it …. you will change the
temperature. Most likely you will change the gradient across the package. Rick 
wrote some papers
back in the 90’s about why this really messes things up…. ( Again this is the 
start of a very long list …).
It’s even longer if you have DAC’s and voltage references external to the OCXO.

So yes, you can get aging a lot of ways. Knowing what is and what is not aging 
can get a bit complicated.

Bob



On Feb 5, 2017, at 3:11 PM, John Ackermann N8UR  wrote:

We know of OCXO that have been continuously running for years and have 
exceptional aging, supposedly as a result.

What does it take to interrupt that? A momentary loss of power?  The oven 
cooling down?  Some long period of off-time?  Or, once the oscillator has baked 
in will it return to that low aging once it has been powered up and thermally 
stabilized?

John
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Re: [time-nuts] OT: Eagle PC CAD now Autodesk, $500/year

[Peter Reilley]

Might I suggest KiCAD?   It is free and open source.   It is developed 
by CERN (https://home.cern/) and
a community of developers.   There are no size limits and it does 
everything that Eagle does.   Available for
Windows and Linux.   CERN uses it in-house and they do a lot of unusual 
projects as you might imagine.

http://kicad-pcb.org/

I had used Eagle and liked it but have moved over to KiCAD after the 
buy-out.


Pete.

On 1/20/2017 11:58 AM, Bob Camp wrote:

Hi

I completely agree that their spin at acquisition and the reality of what just 
came out
is completely amazing. They said they would never do this and that. What they 
are doing
is exactly what they said they would not do.

It’s a rare board that I do in < 4 layers. It’s also quite normal to have 
designs above
160 CM^2. If I have 4 layers, there *will* be signals on all those layers. That 
puts me
squarely in the $500 / yr subscription. A month ago that put me in a perpetual 
license
that I paid < 1/2 that for.

It is not just that the cost has gone up. A number of license “categories” have 
vanished.
The free version is still there, and just as useless for what I do. That’s 
about the only
one that is rational at this point.

So yes, I’m at least as bothered by this as anybody else. What I would suggest 
is to
take a deep breath, sit back, yell at them a bit (along with everybody else 
that has
a license) and see what they do. It is abundantly clear that they have a major 
disconnect
between this and what they have said. There is a lot of explaining for them to 
do. Part of that
could easily be another couple license categories. I’m certainly in no hurry to 
switch
packages.

Right now Fusion 360 is something I use a LOT  more than I use Eagle. This week 
(month .. year)
it is free for me to do that. Why is Fusion free to a basement guy and Eagle 
pay?
That’s not at all clear. Fusion is buggy as can be. Eagle needs some updates. 
Both
have a lot of development $$$ that they will be sucking up. Yes that has to get 
paid
for. It’s not clear that a revenue stream based on hobbyists paying $500 a year
is rational. My guess is Autodesk will figure that out. They may abandon the 
whole
basement thing, they may not …. we’ll see.

Bob



On Jan 19, 2017, at 10:52 PM, Richard (Rick) Karlquist  
wrote:

Off topic, but probably a lot of disgrunted Eagle users on this list.
Its official, you will now have to pay $500 per year for a
professional license from Autodesk.  The spin meistering of the
announcement would make George Orwell proud.  I don't see any way they
can keep me from just using the license I currently own, at least
on the OS's it supports.  (Parenthetically, like many users, I
am also digging in my heels in terms of staying at Windows 7).

Still, the question arises:  are there any affordable alternatives?
Don't have to be entirely free.  I am looking for any trends out
there as to what tool will attract a critical mass of users in
the future.  There is strength in numbers.

Comments?

Rick N6RK
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Re: [time-nuts] Survey plot as art.

[Peter Reilley]

The plots that I posted were of a 48 hour survey but only 32% of the 
survey had completed.


When the survey completes the plot display will disappear.

Pete.


On 1/7/2017 4:34 PM, Bryan _ wrote:

Thanks Pete, I have a Jupiter-T hooked up right now and wanted to see how the 
plot compares to your, unfortunately my antenna position is poor, so will be 
interesting. How many hours did you plot for?


-=Bryan=-



From: time-nuts <time-nuts-bounces+bpl521=outlook@febo.com> on behalf of Peter 
Reilley <preilley_...@comcast.net>
Sent: January 7, 2017 1:15 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Survey plot as art.

You start a precision survey with this command;
sp
You are offered 48 (hour) survey as an option.   I think that you can go
up to 96 hours.
During the survey the scatter plot is displayed.

Pete.



On 1/7/2017 3:32 PM, Bryan _ wrote:

How do you display the survey plot in LH? i.e. the keyboard commands


-=Bryan=-



From: time-nuts <time-nuts-boun...@febo.com> on behalf of Peter Reilley 
<preilley_...@comcast.net>
Sent: January 7, 2017 9:54 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Survey plot as art.


This is the survey from my Trimble NTBW50AA.   It looks like some
bacteria floating around.

The curious thing are the excursions.   Rather than being noise like,
some follow a distinct
path.   But this is only over a few seconds so it seems unlikely that
they are caused by
weather conditions.   The survey from my Resolution T taken at the same
time and using
the same antenna (with a splitter) shows much less orderly excursions
and is more noise
like.


Trimble NTBW50AA survey.


Resolution T survey


Pete.

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Re: [time-nuts] Survey plot as art.

[Peter Reilley]

Another thought, perhaps the difference is between the quality of the 
oscillators.
The Resolution T has an ordinary XO while the NTBW50AA has an OCXO 
(possibly defective).
I would expect the XO to be noise like in a stable temperature 
environment.   The OCXO, if defective,
may have semi-controlled excursions from it's design frequency. However, 
I don't know
if the 10 MHz of the OXCO is used by the GPS chip and could therefore 
affect the calculated

position.

Pete.



On 1/7/2017 4:31 PM, Peter Reilley wrote:
In my case (the original post) there can be no multipath difference, 
same antenna and done at the same time.
The length of the cables from the amplified splitter are about the 
same; within inches.

This must be some difference in the receiver, perhaps in the math?

Pete.

On 1/7/2017 4:16 PM, Bob Camp wrote:

Hi

In terms of multipath at GPS frequencies, a couple of inches is a 
*lot*. Also unless you have
pretty good antennas (as in much larger than 1” each) they will have 
phase issues unique
to each antenna. Phase cancellation and addition is what gives you 
multipath.


Bob


On Jan 7, 2017, at 4:00 PM, Gary E. Miller <g...@rellim.com> wrote:

Yo Bob!

On Sat, 7 Jan 2017 15:16:34 -0500
Bob Camp <kb...@n1k.org> wrote:


The “simple” answer is that the weird legs going out from the central
blob are the result of multi-path / reflections in the received
signal. With enough data you might be able to correlate them to
observed obstructions.

I have lots of data from GPS with the antennas mounted 1 inch apart.
They show different weird legs, so I suspect that local 
geology/architecture

is not the whole story.

For example, compare the plot I just sent, to the one attached here.
Two GPS right next to each other, very differently looking plots.

I'll admit to never generating plots over the same time interval,  I'll
start a 24 hour test of two GPS right now.

RGDS
GARY
--- 


Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] Survey plot as art.

[Peter Reilley]

In my case (the original post) there can be no multipath difference, 
same antenna and done at the same time.
The length of the cables from the amplified splitter are about the same; 
within inches.

This must be some difference in the receiver, perhaps in the math?

Pete.

On 1/7/2017 4:16 PM, Bob Camp wrote:

Hi

In terms of multipath at GPS frequencies, a couple of inches is a *lot*. Also 
unless you have
pretty good antennas (as in much larger than 1” each) they will have phase 
issues unique
to each antenna. Phase cancellation and addition is what gives you multipath.

Bob


On Jan 7, 2017, at 4:00 PM, Gary E. Miller  wrote:

Yo Bob!

On Sat, 7 Jan 2017 15:16:34 -0500
Bob Camp  wrote:


The “simple” answer is that the weird legs going out from the central
blob are the result of multi-path / reflections in the received
signal. With enough data you might be able to correlate them to
observed obstructions.

I have lots of data from GPS with the antennas mounted 1 inch apart.
They show different weird legs, so I suspect that local geology/architecture
is not the whole story.

For example, compare the plot I just sent, to the one attached here.
Two GPS right next to each other, very differently looking plots.

I'll admit to never generating plots over the same time interval,  I'll
start a 24 hour test of two GPS right now.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] Survey plot as art.

[Peter Reilley]

You start a precision survey with this command;
sp
You are offered 48 (hour) survey as an option.   I think that you can go 
up to 96 hours.

During the survey the scatter plot is displayed.

Pete.



On 1/7/2017 3:32 PM, Bryan _ wrote:

How do you display the survey plot in LH? i.e. the keyboard commands


-=Bryan=-



From: time-nuts <time-nuts-boun...@febo.com> on behalf of Peter Reilley 
<preilley_...@comcast.net>
Sent: January 7, 2017 9:54 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Survey plot as art.


This is the survey from my Trimble NTBW50AA.   It looks like some
bacteria floating around.

The curious thing are the excursions.   Rather than being noise like,
some follow a distinct
path.   But this is only over a few seconds so it seems unlikely that
they are caused by
weather conditions.   The survey from my Resolution T taken at the same
time and using
the same antenna (with a splitter) shows much less orderly excursions
and is more noise
like.


Trimble NTBW50AA survey.


Resolution T survey


Pete.

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Re: [time-nuts] Survey plot as art.

[Peter Reilley]

Try again;

Pete.


On 1/7/2017 12:54 PM, Peter Reilley wrote:


This is the survey from my Trimble NTBW50AA.   It looks like some 
bacteria floating around.


The curious thing are the excursions.   Rather than being noise like, 
some follow a distinct
path.   But this is only over a few seconds so it seems unlikely that 
they are caused by
weather conditions.   The survey from my Resolution T taken at the 
same time and using
the same antenna (with a splitter) shows much less orderly excursions 
and is more noise

like.


Trimble NTBW50AA survey.


Resolution T survey


Pete.

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[time-nuts] Survey plot as art.

[Peter Reilley]

This is the survey from my Trimble NTBW50AA.   It looks like some 
bacteria floating around.


The curious thing are the excursions.   Rather than being noise like, 
some follow a distinct
path.   But this is only over a few seconds so it seems unlikely that 
they are caused by
weather conditions.   The survey from my Resolution T taken at the same 
time and using
the same antenna (with a splitter) shows much less orderly excursions 
and is more noise

like.


Trimble NTBW50AA survey.


Resolution T survey


Pete.

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Re: [time-nuts] No sat positions in LH with Trimble NTBW50AA? SOLVED!

[Peter Reilley]

Originally I set the BAUD rate to 19200 with 7 bits and ODD parity 
because that
is what the manual said.   I confirmed these settings using an 
oscilloscope.   With

that, LH mostly worked.

After some of the suggestions here I tried this;
"C:\Program Files (x86)\Heather\heather.exe" /3 /br=9600:8::1 /rxt /gb 
/tz=-5EST/-4DST /vx

This worked perfectly.

It is the BAUD rate that threw me.   I have a lot of experience with 
ASYNC going back to the days
of the ASR33 and ASR35.   I know that some systems were auto-BAUD but 
the manual does not

mention that, I assumed that it was fixed at 19200 which actually did work.

One curious thing that I noticed; previously the clocks differed by 
about 18 seconds between my Resolution T
and my NTBW50AA.   The NTBW50AA agreed with my Win10 machine setup as 
Microsoft installed it.
With the NTBW50AA in Thunderbolt mode, the Res T and the NTBW50AA both 
agree.   Now, only Win10 is

out by about 18 seconds.

Anyway, thanks for all the help,
Pete.




On 1/5/2017 12:41 PM, Mark Sims wrote:

The Nortel devices can talk either as a Thunderbolt or as a SCPI device.  Use 
it as a Thunderbolt (/rxt).   In SCPI mode the satellite positions are polled 
for once a minute (at xx:xx:33).  Thunderbolt mode provides much more and 
better control of the receiver.

---


  I just got my Trimble NTBW50AA GPSDO up and running with Lady Heather 5.0.

However I don't see any satellite data as I do with my Resolution T.   I
am using
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Re: [time-nuts] No sat positions in LH with Trimble NTBW50AA?

[Peter Reilley]

I tried /rxt but that won't communicate.   Must I put the unit in 
Thunderbolt mode?Is there
a jumper or a command that will do it?   The manual that I have does not 
mention different

modes.   It only talks about SCPI.

Thanks,
Pete.



On 1/5/2017 12:41 PM, Mark Sims wrote:

The Nortel devices can talk either as a Thunderbolt or as a SCPI device.  Use 
it as a Thunderbolt (/rxt).   In SCPI mode the satellite positions are polled 
for once a minute (at xx:xx:33).  Thunderbolt mode provides much more and 
better control of the receiver.

---


  I just got my Trimble NTBW50AA GPSDO up and running with Lady Heather 5.0.

However I don't see any satellite data as I do with my Resolution T.   I
am using
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[time-nuts] No sat positions in LH with Trimble NTBW50AA?

[Peter Reilley]

I just got my Trimble NTBW50AA GPSDO up and running with Lady Heather 5.0.
However I don't see any satellite data as I do with my Resolution T.   I 
am using

/rxy which specifies SCPI-(NORTEL) as the device.

What am I doing wrong?

Also, the clock updates every 2 seconds.   I assume that this is an 
artifact of the

2PPS output.

Thanks,
Pete.

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[time-nuts] Resolution T temperature shift at leap second?

[Peter Reilley]

I was running my resolution T at the leap second but LH 5.0 did not capture
the blessed event!   So I don't know how it was reported.

Then I noticed that the temperature took a dive afterwards.   That seems 
odd.

I have only been running this a few weeks and may not have noticed such
occurrences.

Also I notice a tight correlation between the temperature and the rate 
in the graph.
I can't tell which is the cause and which is the effect.When I first 
noticed

this I put the Res T in a small cardboard box to insure that air currents
weren't effecting it.   There was no change in the behavior and no change
in the temperature excursions.   What could this be?

I have attached a screen shot that shows the temperature dive.

Pete.
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Peter Reilley]

You seem to be assuming that the crystal in the TCXO is the same as the 
crystal in the XO.
Wouldn't it be likely that the crystal would be higher quality in the 
more expensive
product; the TCXO?   How would a cheap crystal vs an expensive crystal 
appear different

in the GPS data presented (ignoring the TC part)?

Pete.


On 12/21/2016 7:37 AM, Bob Camp wrote:

Hi


On Dec 21, 2016, at 4:20 AM, Mike Cook  wrote:



Le 21 déc. 2016 à 00:08, Kiwi Geoff  a écrit :

Hello All - and Seasons Greetings,

One of the advantages of the recent hobby drone phenomena - it has
brought to the market a lot of low cost GNSS modules that are
lightweight for drone flight control systems. Those of us with other
hobbies, like "Time Nuts" and RTK - these low cost modules can be a
little goldmine for cost effective toys.

However the dark side is that some vendors are re-badging lower cost
modules, printing their own labels and marking as "Ublox M8N" for
example.

It wouldn't surprise me, but  you have a reference for this?


Can anyone comment on the following data, and whether they think the
oscillator in "my" M8N is a XO or a TCXO ?


I don’t thing that you can get find out from that data. Ublox indicate in the 
product info sheets that the TCXO option is used to get to a first fix quicker 
in weak signal conditions. It is not specified and I think that it is logical, 
that there is an improved timing solution. I would expect that both XO and TCXO 
versions are the same frequency and the better long term stability of a TCXO 
not be an influence on the single shot quantization error of the 1PPS.


The TCXO and XO both have similar short term stability at short tau. The only
advantage to the TCXO is faster time to first fix. If anything the XO will 
“spread”
the quantization error (sawtooth error) better than the TCXO. The TCXO has
more inflections in it’s frequency vs temperature curve. Thus there are more
opportunities for hanging bridges.

In both the TCXO and XO case, the PPS out of the module is based on the
clock edge closest to the PPS estimate. If the clock involved has a period of
20 ns, the error will distribute over ~ +/- 10 ns. The process is identical 
regardless
of the oscillator. The distribution will be the same with both oscillators. As 
long as the
phase noise and short tau ADEV are in spec, the PPS estimate will be the same
in both cases.

Bob




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Re: [time-nuts] 1PPS users?

[Peter Reilley]

There was a discussion here a while ago about synchronizing radio 
telescopes that
were separated by some miles.   The 1PPS from GPS was suggested as a 
possibility.


I am working on a project to do location by triangulation that uses the 
1PPS signal.
I would like to get better than the +-10 nS that the better receivers 
provide.


Pete.


On 12/18/2016 6:16 PM, Bob Stewart wrote:

One thing I've never really understood is who actually uses the high-quality 
1PPS output from a GPSDO.  I have spent a lot of time, effort, and money on 
developing my GPSDO without a whole of thought to the user base.  It was just a 
quest for the best result I could obtain with a particular technology.  The 
frequency standard users was a no brainer.  Everyone who wants a frequency 
standard eventually understands they need to get a GPSDO, or an Rb, or a Cs.  
And that's all I thought I had: a good frequency standard.  And then Tom 
prodded me a bit and showed me the shortcomings of what I was doing, and I did 
something about it.  So, if an NTP user can get his time fix directly from a 
noisy receiver, who actually needs a time-accurate, low jitter 1PPS pulse?
Bob - AE6RV
  -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] Totally unrelated, but..

[Peter Reilley]

Is part of the problem that the level of noise that is of concern is
below what a scope can see anyway: PPB?   If the noise is not narrow
band it might also be not observable using a spectrum analyzer?

Pete.



On 12/7/2016 4:09 AM, Poul-Henning Kamp wrote:


In message , "Van Horn, David" writes:


So what is it that a monolithic regulator (linear) can do which
is not observable on a scope or SA, which would cause a receiver
to think it's getting a signal or significant noise in band?

You have to pay really good attention to specs on some linear regulators,
they are unstable in the weirdest places in the loadmap.

For instance, many regulators really want a specific minimum load, and
if you don't for just a nanosecond, they'll do a hissy fit.

A shunt resistor to ground often solves that, at the cost of 10-20mA.



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[time-nuts] Nutty time-nuttery with WWVB

[Peter Reilley]

I have a few of those "atomic" clocks that receive WWVB to set the time.
However since I live on the east coast they may only pick up the signal
once or twice per year.

Could I implement my own personal WWVB transmitter that would
be powerful enough to be picked up by the clocks in my house?
The signal at 60 KHz might be able to be produced directly by some
sound cards.   With that and a ferrite rod antenna I might get
reliable time elsewhere in my house outside of my lab.

Has anyone tried this?

Pete.

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Re: [time-nuts] Man with too many clocks.

[Peter Reilley]

It is a FE-5680B.   It is my understanding that these were made in many 
variations

of features but that what features were present or absent could not be known
from the model numbers of other external identifying information. This one
has the 1 PPS apparently.

Pete.



On 11/4/2016 1:07 PM, EB4APL wrote:
A bit OT, but regarding your Rb, some units needs to be powered thru 2 
pins, one is used only for the 10 MHz output buffer, if remember it 
correctly. Which is your model number?


Ignacio EB4APL


El 04/11/2016 a las 16:35, Peter Reilley escribió:
I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 
MHz OCXO's that
I have.   The reason that others have pointed out is that the 
uncorrected 1 PPS
signal from the GPS is has just a little too much a jitter to use it 
for calibration
with your eye using a scope.   If it were sawtooth corrected then it 
would be better

but you really need a GPS disciplined oscillator.

Not to be outdone, I brought out a rubidium oscillator that I had put 
away because
it did not appear to work properly.   It only put out a 1 PPS signal 
and nothing else.
I compared that with the GPS PPS and could get a good comparison on 
the scope.
The rubidium drifted about 40 nS over 12 hours.   So it seemed to be 
good.


With that I could adjust the OCXO's in my 5370's.   The spec for the 
HP 5370B with
a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That 
is, it should
take more than 1,000 seconds for one 10 MHz wave to shift by 360 
degrees.   That
is very hard to do using the screw adjustment in the OCXO. Even the 
slightest
movement possible will cause a frequency change greater that is 
spec'ed.   How

do cal labs do it?

My HP 5370A has a 10544 OCXO which is spec'ed for short term 
stability of
better than 1 X 10^11 for 1 second.   Even better than the 5370B! The 
adjustment
screw is much coarser and it is not possible to get any better than a 
few seconds for
one cycle phase shift of the 10 MHz OCXO against the standard. It 
seems that I can't

get even close to the spec.

These have been running for a few days.   It that enough?

Pete.



---
El software de antivirus Avast ha analizado este correo electrónico en 
busca de virus.

https://www.avast.com/antivirus




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Re: [time-nuts] Man with too many clocks.

[Peter Reilley]

I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz 
OCXO's that
I have.   The reason that others have pointed out is that the 
uncorrected 1 PPS
signal from the GPS is has just a little too much a jitter to use it for 
calibration
with your eye using a scope.   If it were sawtooth corrected then it 
would be better

but you really need a GPS disciplined oscillator.

Not to be outdone, I brought out a rubidium oscillator that I had put 
away because
it did not appear to work properly.   It only put out a 1 PPS signal and 
nothing else.
I compared that with the GPS PPS and could get a good comparison on the 
scope.

The rubidium drifted about 40 nS over 12 hours.   So it seemed to be good.

With that I could adjust the OCXO's in my 5370's.   The spec for the HP 
5370B with
a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That 
is, it should
take more than 1,000 seconds for one 10 MHz wave to shift by 360 
degrees.   That
is very hard to do using the screw adjustment in the OCXO.   Even the 
slightest
movement possible will cause a frequency change greater that is 
spec'ed.   How

do cal labs do it?

My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of
better than 1 X 10^11 for 1 second.   Even better than the 5370B! The 
adjustment
screw is much coarser and it is not possible to get any better than a 
few seconds for
one cycle phase shift of the 10 MHz OCXO against the standard.   It 
seems that I can't

get even close to the spec.

These have been running for a few days.   It that enough?

Pete.



On 11/3/2016 8:20 AM, Peter Reilley wrote:
I am the proverbial man with too many clocks and I don't know what 
time it is.

To correct this situation I have decided to calibrate everything.

I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO 
option.   I also
have some TCXO modules.   I figured that I would calibrate them 
against my Trimble

Resolution T GPS receiver.

I put the 1 PPS signal in one channel of my scope and one of the 10 
MHz TCXO
signals in the other channel and look at the phase relationship. The 
TCXO's are
already close enough that I should not be out by more than a fraction 
of a waveform.
I understand that I have to deal with the 1 PPS without sawtooth 
correction.


I expected to see the 10 MHz signal bounce around but not move more 
than 1/2
of a wave length.   Instead I see the 10 MHz waveform appear steady 
for a few seconds
then jump a significant portion of the wave.   The jump is too much to 
be confident

that I have not slipped one cycle.

Can I do what I am trying to do or am I missing something?

Pete.

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Re: [time-nuts] Man with too many clocks.

[Peter Reilley]

Yes you are correct.   All of the devices I am working with have OCXO's, 
it was a type

or a brain short.

Pete.



On 11/3/2016 9:07 PM, Paul Alfille wrote:

By the way, the HP5370B has a OCXO, not TCXO. It needs a while to become
stable, but should be quite consistent after that.

On Thu, Nov 3, 2016 at 4:50 PM, Nick Sayer via time-nuts <time-nuts@febo.com

wrote:
I’m going to try and describe my thoughts, but it may not come out as
“right” as some others here can do. Still…

One problem you’re going to run into if you go down the road of attempting
to PLL one thing to another is that you have to find a balance between
phase control and frequency stability.

You’re going to always be reacting to the phase drift of your disciplined
device. Your “knob” for doing so is to adjust (probably in steps) the
frequency. If your PLL is very “twitchy,” then you’re going to move that
knob very quickly and firmly, resulting in very tight phase control, but a
frequency that, at least over a short term, will jump around a bit.

By contrast, if you are very reluctant to move the “knob,” then you’re
going to move it so slowly that by the time you have a meaningful effect on
the phase, the phase will have drifted quite a bit. That said, your
movement of the frequency knob will be so slow that the frequency stability
would be much better, at least over the short term.

In essence, this is choosing the PLL time constant. How you do so depends
on the behavior of your device as well as the stability you desire from the
output.


On Nov 3, 2016, at 5:20 AM, Peter Reilley <preilley_...@comcast.net>

wrote:

I am the proverbial man with too many clocks and I don't know what time

it is.

To correct this situation I have decided to calibrate everything.

I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.

  I also

have some TCXO modules.   I figured that I would calibrate them against

my Trimble

Resolution T GPS receiver.

I put the 1 PPS signal in one channel of my scope and one of the 10 MHz

TCXO

signals in the other channel and look at the phase relationship. The

TCXO's are

already close enough that I should not be out by more than a fraction of

a waveform.

I understand that I have to deal with the 1 PPS without sawtooth

correction.

I expected to see the 10 MHz signal bounce around but not move more than

1/2

of a wave length.   Instead I see the 10 MHz waveform appear steady for

a few seconds

then jump a significant portion of the wave.   The jump is too much to

be confident

that I have not slipped one cycle.

Can I do what I am trying to do or am I missing something?

Pete.

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Re: [time-nuts] Man with too many clocks.

[Peter Reilley]

I am using the 1 PPS for the trigger.

Pete.


On 11/3/2016 8:59 AM, Antonio A. S. Magalhaes wrote:


Pete,

Tell us about your trigger: where is it?

Regards,

Antonio/CT1TE

---

A 2016-11-03 12:20, Peter Reilley escreveu:

I am the proverbial man with too many clocks and I don't know what 
time it is.

To correct this situation I have decided to calibrate everything.

I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO 
option.   I also
have some TCXO modules.   I figured that I would calibrate them 
against my Trimble

Resolution T GPS receiver.

I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
signals in the other channel and look at the phase relationship. The 
TCXO's are
already close enough that I should not be out by more than a fraction 
of a waveform.

I understand that I have to deal with the 1 PPS without sawtooth correction.

I expected to see the 10 MHz signal bounce around but not move more than 1/2
of a wave length.   Instead I see the 10 MHz waveform appear steady 
for a few seconds
then jump a significant portion of the wave.   The jump is too much 
to be confident

that I have not slipped one cycle.

Can I do what I am trying to do or am I missing something?

Pete.

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[time-nuts] Man with too many clocks.

[Peter Reilley]

I am the proverbial man with too many clocks and I don't know what time 
it is.

To correct this situation I have decided to calibrate everything.

I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO 
option.   I also
have some TCXO modules.   I figured that I would calibrate them against 
my Trimble

Resolution T GPS receiver.

I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
signals in the other channel and look at the phase relationship. The 
TCXO's are
already close enough that I should not be out by more than a fraction of 
a waveform.

I understand that I have to deal with the 1 PPS without sawtooth correction.

I expected to see the 10 MHz signal bounce around but not move more than 1/2
of a wave length.   Instead I see the 10 MHz waveform appear steady for 
a few seconds
then jump a significant portion of the wave.   The jump is too much to 
be confident

that I have not slipped one cycle.

Can I do what I am trying to do or am I missing something?

Pete.

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Re: [time-nuts] So what’s inside that Cs Beam Tube anyway?

[Peter Reilley]

Just throwing this out: would it be possible recover the cesium by heating
the tube but cooling it near where the reservior is?   This might cause the
cesium to migrate in that direction and some of it end up in the reservior?

Pete.

On 11/2/2016 11:38 AM, paul swed wrote:

Oh yes and guess which tubes we find? The 40 year olds at ham prices. :-)
At least thats what I have.
Like your comment as so far what I have learned is that seems like other
things going on.
I sort of believe its C pollution of things like the ionizer and even the
photo tube elements over time. Its a curiosity without much of a way to
prove it.

Regards
Paul
WB8TSL

On Wed, Nov 2, 2016 at 10:53 AM, Richard (Rick) Karlquist <
rich...@karlquist.com> wrote:


This has probably been covered here before, but, at least going
to the 5071A, now 25 years ago!, all CBT's, whether high
performance or not, have the same amount of cesium inside.
This means that the standard performance (never call it
"low" performance) CBT has enough cesium to last 30 years!
Thus for those tubes, we can rule out cesium replenishment
even if it were possible.

Rick


On 11/1/2016 8:38 PM, Mark Sims wrote:


You mean I can't just drill a hole in,  wash out the old cesium with some
tap water ;-),  toss in some new cesium, suck out the air,  bung a cork in
the hole, and call it a day?   Drat! foiled again...

---

Because it's not that easy. We are talking about a high vacuum system

here.


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Re: [time-nuts] our favorite topics

[Peter Reilley]

Please don't take this wrong but your use of the word "treaty" is wrong.
I think you mean "treatise".

Pete.

On 10/29/2016 8:05 PM, Attila Kinali wrote:

Hoi Ulrich,

On Sat, 29 Oct 2016 19:56:53 -0400
KA2WEU--- via time-nuts  wrote:


The Parzen book was on my list (Amazon ), I find these books,  including
Rhea's book practically useless as they do not provide the necessary  non
-linear noise analysis, and do not have real live examples with test data.
Cerda's "Understanding Quartz Crystals and Oscillators book I have not  seen.

You don't have to look then. There are very few people who actually looked
at the noise in oscillator circuits and tried to optimize it. You and
Poddar are definitely those who wrote most about it. Then comes probably
Enrico. One can find a paper here and there analysing different noise
sources, but never a complete treaty.

The lack of noise/non-linear analysis does not mean you cannot learn
from those books, though. They are good books to learn from on how to
build an oscillator. Once that is achieved, one can learn how to make
it low noise by reading your books :-)

Attila Kinali



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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

More information;

I added a picture to the dropbox from my Flir IR camera.   The picture 
shows the copper block
that the crystal is attached to running at about 200 F.   In the IR shot 
the copper block is to the
right.In most of the regular pictures it is toward the bottom of the 
picture.This is with the
unit (minus the S30 chip) running on 5 volts for more than 10 hours.   
Is that too hot?


While running at 5 volts the current is constant at about 4. amps, no 
cycling.   At 12 volts
it cycled between .9 to .1 amps.   I would not expect cycling for the 
temperature control

of an OCXO.   I would expect a linear temperature control circuit.

I looked at the tantalum capacitor on the bottom of the board.   The 
marking is 39-10.
Does that mean 39 uF and 10 volts?   If so then it must be a 5 volt 
unit.   The capacitor

did not explode at 12 volts.

Dropbox link:
https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?dl=0

Pete.

On 10/18/2016 9:11 AM, Peter Reilley wrote:
I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at 
the MIT flea market.
As expected it was dead.   It heats up as expected but looking at the 
output with a scope there
is nothing.   However looking at the output with a spectrum analyzer I 
can see a faint 10 MHz
signal.   It seems that the oscillator is running but the output 
circuitry is dead.   Reasonable

assumption?

Anyway, has anyone had any luck unsoldering the tin case without 
destroying it?


Pete.

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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

Not S05 but S30.   A 74S30 is an 8 input NAND and the foot pint on the 
board, looking

at the inputs and outputs, seems to confirm it.

There is no 5 volt regulator.   The power pin is connected directly to 
the power

pin of a 74S30.

Pete.

On 10/28/2016 6:50 PM, J. L. Trantham wrote:

I have emailed Peter separately earlier today.

The top side marking of the chip appears to indicate it is a TI 74LS05D.

The datasheet is here:

http://www.ti.com/lit/ds/symlink/sn74ls05.pdf

If it is indeed a 'HEX Inverter', perhaps another 'channel' can be wired in 
place to see if it would work without having to find another chip.

Also, I, too, was wondering if it was 5 V or if there was a 5 V regulator on 
the board somewhere.

Hope this helps.

Joe



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Miller
Sent: Friday, October 28, 2016 4:18 PM
To: pe...@reilley.com; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Opening an Isotemp OCXO

Can you see the voltage on the yellow dipped tantalum under the board? I think 
that is what it is.


- Original Message -
From: "Peter Reilley" <preilley_...@comcast.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Friday, October 28, 2016 3:28 PM
Subject: Re: [time-nuts] Opening an Isotemp OCXO



That seems the most reasonable thing to do.

Pete


On 10/28/2016 3:20 PM, Tom Miller wrote:

It looks like that is the only device that could be damaged by 12 volts.
Can you find a replacement and try running at 5 volts?


- Original Message - From: "Peter Reilley"
<preilley_...@comcast.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Friday, October 28, 2016 3:10 PM
Subject: Re: [time-nuts] Opening an Isotemp OCXO



The reason that there was 12 volts on the unit was because I put it
there. I should
have tried 5 volts first but the only datasheet that I could find said
12 volts.
All the eBay units that look the same say 12 volts.

Pete.

On 10/28/2016 12:53 PM, paul swed wrote:

I confirmed the pin out matches a 74s30 also. An S30 is TTL. Great pix
to
look at.
So 12 V on a 5 V chip is indeed a smoker. Find out why there was 12 V.
OK crazy talk I see a 1K resistor next to the VCC chip. Would anyone be
crazy enough to use a dropping resistor from 12 V to get 5?? Really bad
engineering and I don't actually believe they would. But if true a open
74s30 would indeed show 12 V on pin 14.
Good luck.
Paul
WB8TSL

On Fri, Oct 28, 2016 at 12:48 PM, jimlux <jim...@earthlink.net> wrote:


On 10/28/16 9:13 AM, Scott Stobbe wrote:


The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also be
a
blown regulator in your ocxo, if it is indeed a 12v model.

There you go..the design could use a 74S30 as a driver - it's fast,

fairly good drive, but runs off 5V.  If the regulator is shorted, and
you
put 12V on it, it will cook.


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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

That seems the most reasonable thing to do.

Pete


On 10/28/2016 3:20 PM, Tom Miller wrote:
It looks like that is the only device that could be damaged by 12 
volts. Can you find a replacement and try running at 5 volts?



- Original Message - From: "Peter Reilley" 
<preilley_...@comcast.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts@febo.com>

Sent: Friday, October 28, 2016 3:10 PM
Subject: Re: [time-nuts] Opening an Isotemp OCXO


The reason that there was 12 volts on the unit was because I put it 
there. I should
have tried 5 volts first but the only datasheet that I could find 
said 12 volts.

All the eBay units that look the same say 12 volts.

Pete.

On 10/28/2016 12:53 PM, paul swed wrote:
I confirmed the pin out matches a 74s30 also. An S30 is TTL. Great 
pix to

look at.
So 12 V on a 5 V chip is indeed a smoker. Find out why there was 12 V.
OK crazy talk I see a 1K resistor next to the VCC chip. Would anyone be
crazy enough to use a dropping resistor from 12 V to get 5?? Really bad
engineering and I don't actually believe they would. But if true a open
74s30 would indeed show 12 V on pin 14.
Good luck.
Paul
WB8TSL

On Fri, Oct 28, 2016 at 12:48 PM, jimlux <jim...@earthlink.net> wrote:


On 10/28/16 9:13 AM, Scott Stobbe wrote:

The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also 
be a

blown regulator in your ocxo, if it is indeed a 12v model.

There you go..the design could use a 74S30 as a driver - it's fast,
fairly good drive, but runs off 5V.  If the regulator is shorted, 
and you

put 12V on it, it will cook.


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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

I don't know, I looked for a name and could not find one.
Sometimes there is no substitute for a big block of copper when soldering.
I pick them up at flea markets, no one wants them.   I have a few.

Pete.

On 10/28/2016 12:27 PM, Adrian Godwin wrote:

That's one sweet soldering iron. Is it an American Beauty ?




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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

The reason that there was 12 volts on the unit was because I put it 
there.   I should
have tried 5 volts first but the only datasheet that I could find said 
12 volts.

All the eBay units that look the same say 12 volts.

Pete.

On 10/28/2016 12:53 PM, paul swed wrote:

I confirmed the pin out matches a 74s30 also. An S30 is TTL. Great pix to
look at.
So 12 V on a 5 V chip is indeed a smoker. Find out why there was 12 V.
OK crazy talk I see a 1K resistor next to the VCC chip. Would anyone be
crazy enough to use a dropping resistor from 12 V to get 5?? Really bad
engineering and I don't actually believe they would. But if true a open
74s30 would indeed show 12 V on pin 14.
Good luck.
Paul
WB8TSL

On Fri, Oct 28, 2016 at 12:48 PM, jimlux  wrote:


On 10/28/16 9:13 AM, Scott Stobbe wrote:


The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also be a
blown regulator in your ocxo, if it is indeed a 12v model.

There you go..the design could use a 74S30 as a driver - it's fast,

fairly good drive, but runs off 5V.  If the regulator is shorted, and you
put 12V on it, it will cook.


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and follow the instructions there.

Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

There is no regulator in the unit.   The power pin is connected directly 
to the S30 chip.


Pete.


On 10/28/2016 1:31 PM, J. L. Trantham wrote:

Have you measured the voltage on the 'power' pin for the chip with 12 V applied 
to the OCXO (or 5 V applied)?

Is there a 5 V regulator on the board?

Joe

-Original Message-
From: Peter Reilley [mailto:preilley_...@comcast.net]
Sent: Friday, October 28, 2016 9:11 AM
To: J. L. Trantham
Subject: Re: [time-nuts] Opening an Isotemp OCXO

Thanks for the link.   I did not find any S30 chips that would run off
12 volts.

Could the whole OCXO be a 5 volt unit?

Pete.


On 10/28/2016 9:53 AM, J. L. Trantham wrote:

Peter,

Thanks for the update.

No time to spend right now but I found this by googling 'TI S30 SOIC chip'

http://www.ti.com/packaging/docs/partlookup.tsp#divline

Hope it helps.

Joe

-Original Message-
From: Peter Reilley [mailto:preilley_...@comcast.net]
Sent: Friday, October 28, 2016 8:24 AM
To: J. L. Trantham
Subject: Re: [time-nuts] Opening an Isotemp OCXO

I did finally get it open.   I used a very large old style soldering
iron and .003 inch steel
shim stock.   I would melt the solder on the straight seams and insert
small pieces of
the shim.   Solder does not stick well to steel so the shim kept the
soldered seam open.
I used a soldering iron rather than a torch because I can control the 
temperature.

I could not use the shim at the corners.   After all the straight seams
were separated
I could pull each corner using a screw in the mounting hole and melt the solder 
at
the corner.   Slowly working my way around, corner by corner, I got it
opened.   I did
not damage anything so I should be able to close it up after I fix it.

Looking around with my scope it seems that the output driver chip is bad as I 
expected.
It is a TI 14 pin surface mount DIP.   It says S30 on it which if it is
a 74S30 it is an
8 input positive NAND gate.   The board layout confirms this as the 10
MHz signal is
connected to pin 2 and all other inputs are tied high.   Pin 8 is
connected to the output.
The chip is run off 12 volts so it must be CMOS.   But I cannot find any
chip like that
that will run off 12 volts.   Any suggestions for a replacement?

Also, using an 8 input NAND chip for a driver seems an odd choice.

When I put 12 volts on the unit the S30 chip gets really hot. After I removed 
the chip
the unit seems to work OK.   The current jumps between about .1 amp to
.9 amps.   It seems
like the temperature regulator is an on/off type controller.

The device on eBay, item 261920574725, looks exactly like what I have.

I have placed a bunch of pictures in my dropbox.
https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?d
l=0

Pete.


On 10/18/2016 10:57 AM, J. L. Trantham wrote:

Pete,

I'm not familiar with your OCXO but I found one shown on 'theBay' (item  
261920574725) and it appeared to have an option for 'mounting screws', four of 
them, on the bottom.  Interestingly, the 'link' to the datasheet for that unit 
did not show threads for mounting screws.

If your unit has that option, I would suggest placing four long screws, 
mounting the item in a vise, use a small torch (I've used a hand held propane 
torch turned down very low to open a number of units from 5061A's) around the 
bottom of the case while gripping the top with an appropriate sized Channel 
Lock plier and lifting off the top.

If you can repair the OCXO, it should be easy to reassemble the unit with 
solder.

TheBay unit looks like it has a screw cover (which likely has a rubber gasket) 
for mechanical adjustment of the frequency.  I'd remove that before applying 
the torch. :^).

If you get it open, I'd love to see some pictures of the insides.

Good luck and hope this helps.

Joe



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
Peter Reilley
Sent: Tuesday, October 18, 2016 8:11 AM
To: time-nuts@febo.com
Subject: [time-nuts] Opening an Isotemp OCXO

I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at the MIT 
flea market.
As expected it was dead.   It heats up as expected but looking at the
output with a scope there
is nothing.   However looking at the output with a spectrum analyzer I
can see a faint 10 MHz
signal.   It seems that the oscillator is running but the output
circuitry is dead.   Reasonable
assumption?

Anyway, has anyone had any luck unsoldering the tin case without destroying it?

Pete.

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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

There is no regulator chip in the unit.   I am thinking that this must
be a 5 volt unit.

Pete.

On 10/28/2016 12:42 PM, Dan Rae wrote:

On 10/28/2016 9:09 AM, Peter Reilley wrote:

The only document that I could find said 12 volt.

Pete.
The 82 series came in a lot of flavors.  I have one 82-49 which is 
definitely 12V ( draws 0.12A when warm and maybe 0.3 when cold) and 
has a 5V pp square wave output at 10 MHz.  It also has a Vref output 
and an EFC input.  What is odd about this one is that it came to me 
from a TRW swap meet scrap dealer who bought stuff from Cubic 
Communications in San Diego and it had a "Reject" tag from them. 
Probably because it was supposed to be a 5 MHz unit as marked, so 
presumably had the wrong crystal fitted by Isotemp. Other versions of 
the 82 series (-10) were fitted to Racal Receivers like the 
RA6790/GM.  Screw adjustment on the side and 5 MHz output.


Are you sure yours shouldn't have a 5V supply on that output IC? Could 
be why it died if there is an internal regulator that failed putting 
the full supply voltage on the IC?


Dan





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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

The only document that I could find said 12 volt.

Pete.


On 10/28/2016 11:49 AM, Poul-Henning Kamp wrote:


In message <10a3ea7d-37f0-51bc-2470-35645d767...@comcast.net>, Peter Reilley 
writes:


The chip is run off 12 volts so it must be CMOS.

Or the OCXO is not a 12V model ?




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Re: [time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

I did finally get it open.   I used a very large old style soldering
iron and .003 inch steel shim stock.   I would melt the solder on the
straight seams and insert small pieces of the shim.   Solder does not
stick well to steel so the shim kept the soldered seam open.
I used a soldering iron rather than a torch because I can control the
temperature.

I could not use the shim at the corners.   After all the straight seams
were separated I could pull each corner using a screw in the mounting
hole and melt the solder at the corner.   Slowly working my way around,
corner by corner, I got it opened.   I did not damage anything so I
should be able to close it up after I fix it.

Looking around with my scope it seems that the output driver chip is bad
as I expected.   It is a TI 14 pin surface mount DIP.   It says S30 on it
which if it is a 74S30 it is an 8 input positive NAND gate.   The board
layout confirms this as the 10 MHz signal is connected to pin 2 and all
other inputs are tied high.   Pin 8 is connected to the output.

The chip is run off 12 volts so it must be CMOS.   But I cannot find any
chip like that that will run off 12 volts.   Any suggestions for a replacement?

Also, using an 8 input NAND chip for a driver seems an odd choice.

When I put 12 volts on the unit the S30 chip gets really hot. After I
removed the chip the unit seems to work OK.   The current jumps between
about .1 amp to .9 amps.   It seems like the temperature regulator is
an on/off type controller.

The device on eBay, item 261920574725, looks exactly like what I have.

I have placed a bunch of pictures in my dropbox.
https://www.dropbox.com/sh/52e9d1rva9kpb3w/AABmbIj1aK7Zk2J9SNMmu-JAa?dl=0

Pete.



On 10/18/2016 10:57 AM, J. L. Trantham wrote:

Pete,

I'm not familiar with your OCXO but I found one shown on 'theBay' (item  
261920574725) and it appeared to have an option for 'mounting screws', four of 
them, on the bottom.  Interestingly, the 'link' to the datasheet for that unit 
did not show threads for mounting screws.

If your unit has that option, I would suggest placing four long screws, 
mounting the item in a vise, use a small torch (I've used a hand held propane 
torch turned down very low to open a number of units from 5061A's) around the 
bottom of the case while gripping the top with an appropriate sized Channel 
Lock plier and lifting off the top.

If you can repair the OCXO, it should be easy to reassemble the unit with 
solder.

TheBay unit looks like it has a screw cover (which likely has a rubber gasket) 
for mechanical adjustment of the frequency.  I'd remove that before applying 
the torch. :^).

If you get it open, I'd love to see some pictures of the insides.

Good luck and hope this helps.

Joe



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Reilley
Sent: Tuesday, October 18, 2016 8:11 AM
To: time-nuts@febo.com
Subject: [time-nuts] Opening an Isotemp OCXO

I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at the MIT 
flea market.
As expected it was dead.   It heats up as expected but looking at the
output with a scope there
is nothing.   However looking at the output with a spectrum analyzer I
can see a faint 10 MHz
signal.   It seems that the oscillator is running but the output
circuitry is dead.   Reasonable
assumption?

Anyway, has anyone had any luck unsoldering the tin case without destroying it?

Pete.

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[time-nuts] Opening an Isotemp OCXO

[Peter Reilley]

I bought an Isotemp OCXO82-59 with a frequency of 10 MHz for a $3 at the 
MIT flea market.
As expected it was dead.   It heats up as expected but looking at the 
output with a scope there
is nothing.   However looking at the output with a spectrum analyzer I 
can see a faint 10 MHz
signal.   It seems that the oscillator is running but the output 
circuitry is dead.   Reasonable

assumption?

Anyway, has anyone had any luck unsoldering the tin case without 
destroying it?


Pete.

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Re: [time-nuts] GPSDO - probably a stupid question.

[Peter Reilley]

You can get crystal oscillators that have a frequency control signal and 
are more
stable than the run of the mill oscillators.   Changing the GPS 
oscillator would
require modifying a very tightly populated circuit board.   Perhaps not 
possible.


What about some of the SDR (software defined radio) projects that aim to
implement GPS functionality?   If you used the GPS chipping rate (1.023 MHz)
to dicipline the 10 MHz oscillator then you are less sensitive to 
crystal instabilities.
You are updating the crystal one million times a second rather than once 
per second.
This is assuming that the chipping rate of the transmitter is just as 
good as the

1 PPS signal.   This info from here;
https://www.e-education.psu.edu/geog862/node/1753
and here;
https://en.wikipedia.org/wiki/GPS_signals

Even using the 50 bits/sec data rate of the GPS signal would allow 
updating the

GPSDO faster than the 1 PPS signal.

Pete.
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[time-nuts] GPSDO - probably a stupid question.

[Peter Reilley]

As a neophyte, I was wondering: rather that trying to discipline an external
oscillator to create a GPSDO and produce a precise 10 MHz why not 
discipline the oscillator
of the GPS receiver itself?   This could be done with a varactor diode 
across crystal of the
receiver's oscillator.   Of course there are the same problems with 
trying to servo this
oscillator as there are trying to servo an external oscillator but there 
are fewer parts.


Being a beginner I assume that I am missing something, but what?

Thanks,
Pete.

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Re: [time-nuts] Q/noise of Earth as an oscillator

[Peter Reilley]

If you consider viewing earth from above the equator at a long distance 
and imagine a
spot on the surface of the earth.   That spot will appear to have a 
sinusoidal motion.
The frequency of the sinusoid exhibits a decay.   That decay can be 
considered as the Q

of the earths rotation.

Pete.



On 7/27/2016 9:00 AM, jimlux wrote:

On 7/27/16 5:43 AM, Michael Wouters wrote:

On Wed, Jul 27, 2016 at 8:08 AM, Attila Kinali  wrote:

"I am not sure you can apply this definition of Q onto earth."

It  doesn't make sense to me either.

If you mark a point on the surface of a sphere then you can observe
that point as the sphere
rotates and count rotations to make a clock. If you think of just a
circle, then a point on it viewed in a rectilinear coordinate system
executes simple harmonic motion so the motion of that point looks like
an oscillator, so that much is OK.

But unlike the LCR circuit, the pendulum and quartz crystal, the
sphere's rotational motion does not have a
resonant frequency. Another way of characterizing the Q of an
oscillator, the relative width of the resonance, makes
no sense in this context.



There's also the thing that "things that resonate" typically have 
energy transferring back and forth between modes or components: E 
field and H field for an antenna; kinetic vs potential energy for 
pendulums and weight/spring; charge and current (C & L, really E 
field/H field again).


Spinning earth is more of an "rotational inertia and loss" thing, with 
zero frequency, just the exponential decay term.


If you think of a single measurand in any of these scenarios you have 
at the core some sort of exp(-kt)*cos(omega*t+phi) and we're relating 
Q to the coefficient k.



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Re: [time-nuts] Pages on 5650-option-58

[Peter Reilley]

Jim;

I found this;

https://www.febo.com/pipermail/time-nuts/2008-June/031663.html

and this;

http://www.leapsecond.com/museum/fei5650a/


Pete.


On 6/21/2016 1:02 PM, James Robbins wrote:

Hello Bill,

  


I was reading an old note by you on Time-Nuts (April 7, 2013) where you
refer to a .zip file of materials on the 5650 rubidium oscillators.  There
was a link to the zip folder

(http://pages.suddenlink.net/stevewingate/cryptic1/for alec on
5650-option-58.zip
 ) which doesn't work any longer.  Would you have an alternative
link to the material.  I am soing some work with FE-5650A and FE-5658A
oscillators.

  


Many thanks.

  


Jim Robbins

N1JR

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Re: [time-nuts] GENIUS by Stephen Hawking (PBS TV), with 5071A cesium clocks

[Peter Reilley]

I have a question.   I, of small brain, am wondering: if the time 
difference between the
top of the mountain and the bottom of the mountain is 20 nS over 24 
hours could you
repeat the same experiment using GPS?The time difference of 20 nS is 
measurable

using GPS.

The GPS clock must run faster on the mountain top than the GPS at the 
mountain
base and yet the two remain synchronized to the satellite reference.   
Therefore
the GPS 1 PPS signal (measurable to a few nS) must be wrong in in one of 
the local

frame references.

My brain hurts.

Pete.


On 5/20/2016 10:16 AM, Bob Camp wrote:

Hi

Ok, so *that* link got me to the episode. Very impressive stuff. Well done !!!

Bob



On May 20, 2016, at 2:04 AM, Tom Van Baak  wrote:

For those of you who missed the live TV broadcast, I'm told PBS has a live 
stream:
http://www.pbs.org/video/2365757267/

The cesium clock parts are in the last 15 minutes of the show.
I also added more photos/plots to:
http://leapsecond.com/great2016a/photos.htm

/tvb
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Re: [time-nuts] LIGO detects gravitational waves

[Peter Reilley]

I am curious about the final stages.   When they are far apart they are 
outside of

each others event horizon (the boundary from which nothing can escape).   As
they wind down the event horizons will merge but not be spherical. They are
hot spherical since the two singularities at their center have not 
merged.   How

long did it take from the time that the event horizons touched to when the
singularities merged?

Where did the energy of the gravity wave come from?   Three solar masses
of energy from what they say.   My understanding is that the 2 black holes
started orbiting at some distance and were moving at slow speed. As they 
wound
down they picked up speed, ultimately gaining a significant portion of 
light speed.

This must have increased their apparent mass.   Is this increase in mass the
same mass that they ultimately lost in radiating the gravity waves?

Once the event horizons merged the singularities continued to orbit each
other and radiate gravity waves.   But since the amplitude of the gravity
waves goes down as the spacing decreases will the singularities ever
actually merge?   They are infinitely small, so can they ever occupy the
same position and merge?

Pete.

On 2/13/2016 7:14 PM, Bob Camp wrote:

Hi

At least my simple take on it:

As they get closer, the rotation speeds up. It is no different than the ice 
skater
pulling in their arms.

Once they get close enough, there are no longer two black holes. They have 
become a
single black hole. They now radiate a “dc signal” that the detector can’t deal 
with.

Bob


On Feb 13, 2016, at 6:34 PM, Bill Hawkins  wrote:

IMHO, the decay seems backwards because we are watching the growth of
the event as the black holes approach each other, reaching a maximum at
collision.

Don't know why the signal drops off after the collision. May be because
gravity stops changing, or maybe because the resulting object left the
universe - well, not if mass and energy are conserved. Or did the wave
contain all of the radiated energy?

Disclaimer: My field of study was not physics.

Bill Hawkins

-Original Message-
From: Bob Stewart
Sent: Saturday, February 13, 2016 2:35 PM

Hi Tom,

Thanks for posting this.  I'm looking at the timelab plot, and the only
thing I can relate that to is a musical note played backward.  IOW, the
decay seems backwards to me.

Bob - AE6RV


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Re: [time-nuts] low noise multiplication to 100 MHz

[Peter Reilley]

Have you considered synthesizers?   I am using an Analog Devices AD9517 
to drive a A/D
converter at 250 MHz.   It has many clock outputs that are independently 
configurable.

It is intended for low jitter applications.

Pete.

On 1/21/2016 9:43 AM, jimlux wrote:
My tiny 100 MHz low noise OCXOs are unexpectedly delayed at the mfr, 
and I'm looking at alternative schemes.
One is to get 10 or 20 MHz OCXOs (typically in stock) and multiply 
them up. I've got the Wenzel ap notes on 2diode and using HCMOS (and 
I've used the packaged Wenzel multipliers), and I think I have some 
spare board real estate on another board.


The 2diode multiplier describes using 1n5711 or 1n914, but I was 
wondering if anyone has run this sort of multiplier up to 100 MHz?


What sort of symmetry does the resulting waveform have (yeah, it's 
basically a filtered sinewave, because you're picking a harmonic, but 
I've been surprised before)?





I'm driving an FPGA and a couple of ADCs.  The ADCs have differential 
input that is 10kohms with 9pF in parallel offset from ground in the 
usual way (we're using a transformer and appropriate bias resistors). 
Not a 50 ohm load, in any case.  And it wants a clock that is high for 
about 47.5% to 52.5% in one mode and much wider (30%-70% in another).. 
I need to check.


The FPGA is less critical noise-wise, and has a AD8138 buffer in any 
case, which can fix a variety of evils.




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Re: [time-nuts] The Pendulum Paradigm by Martin Beech, 2014

[Peter Reilley]

I had no idea that so many aspects of this had been researched.   I thought
that pendulums were yesterday's technology.

Pete.

On 10/28/2015 1:03 PM, Tom Van Baak wrote:

Hi Pete,

Yes, if you measure well enough, every mechanical clock reveals periodic 
variations from imperfections in its gears, the balance of the hands, changes 
in spring tension, and environmental changes such as temperature, humidity and 
air pressure. It shows up in spectral plots, in Allan deviation plots, as well 
as the time and rate plots. Some examples here:

http://leapsecond.com/pend/clockb/
http://leapsecond.com/ten/

Add earthquakes to the list of what a pendulum clock will detect:

http://bmumford.com/mset/tech/quake/

Most people use this system to measure their pendulum clocks:
http://bmumford.com/mset/

As for pendulum clocks and gravity, yes, the very best pendulum clocks in the 
world are stable enough to reveal the changes in the acceleration of gravity 
due to the periodic motions of our earth-sun-moon. For details see:

http://leapsecond.com/hsn2006/
http://leapsecond.com/pend/shortt/

/tvb


- Original Message -
From: "Peter Reilley" <preilley_...@comcast.net>
To: <time-nuts@febo.com>
Sent: Wednesday, October 28, 2015 7:23 AM
Subject: Re: [time-nuts] The Pendulum Paradigm by Martin Beech, 2014



I have been pondering pendulum clocks.   I was wondering what the ADEV of a
pendulum would show.   I assume that you could see the errors in the
gear train.
You should see the period of each gear.   You should see the spring wind
down
and being rewound.

Further, would you be able to see the phase of the moon and the tides?
This
is using the pendulum as a gravimeter.   Would it be sensitive enough
for that?

(have to stop my mind from wandering.)

Pete.

On 9/19/2015 7:15 PM, Brooke Clarke wrote:

Hi:

I just started reading the subject book where the mathematics of the
pendulum are used as a unifying idea to tour physics.
Included is a correct illustration on page 205 of Foucault's gyroscope
demonstration that the earth turns 360 degrees in a sidereal day.

Maybe there will be a reference to a gyroscope as a pendulum that's
making full circles rather than swinging back and forth.

Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
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Re: [time-nuts] The Pendulum Paradigm by Martin Beech, 2014

[Peter Reilley]

I have been pondering pendulum clocks.   I was wondering what the ADEV of a
pendulum would show.   I assume that you could see the errors in the 
gear train.
You should see the period of each gear.   You should see the spring wind 
down

and being rewound.

Further, would you be able to see the phase of the moon and the tides?   
This
is using the pendulum as a gravimeter.   Would it be sensitive enough 
for that?


(have to stop my mind from wandering.)

Pete.

On 9/19/2015 7:15 PM, Brooke Clarke wrote:

Hi:

I just started reading the subject book where the mathematics of the 
pendulum are used as a unifying idea to tour physics.
Included is a correct illustration on page 205 of Foucault's gyroscope 
demonstration that the earth turns 360 degrees in a sidereal day.


Maybe there will be a reference to a gyroscope as a pendulum that's 
making full circles rather than swinging back and forth.


Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
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Re: [time-nuts] My HP 5370B reads 6 nS out!

[Peter Reilley]

I have installed TimeLab and am getting good results.   But I have
a question on how to setup my HP 5379B.

There are separate trigger level settings for start and stop.   In
my case I want to measure the period of the 1 PPS signal from my
Resolution T.   If the start and stop trigger levels are not EXACTLY
the same then won't the period measurement be wrong.   It seems
that using only the start trigger level for both start and stop
would be the correct way of doing it.

While TimeLab was running I adjusted both the start and stop trigger
levels.   It is clear that they both are setting their respective
trigger points.   Doesn't this effect the period measurement results? 

My setup;
1 PPS signal from GPS connected to start input.
Positive slope trigger both channels.
50 Ohm both channels.
Divide by 1 both channels.
DC coupling both channels.
Start switch set to COM.
Trigger level knobs set to where the trigger is consistent on both channels.


Thanks,
Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter
Reilley
Sent: Tuesday, June 16, 2015 12:46 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] My HP 5370B reads 6 nS out!

Bob;

It seems reasonable to calibrate my 5370B using the 1 PPS signal from my
Resolution T and assume that my rubidium oscillator is 6 X 10^-9 off.
There is no reason to believe that the GPS 1 PPS signal is wrong.

The FEI FE-5680A devices seem to be hard to determine what options they
actually have.   Perhaps it just needs calibration.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Tuesday, June 16, 2015 7:02 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] My HP 5370B reads 6 nS out!

Hi
 On Jun 15, 2015, at 9:51 PM, Peter Reilley pe...@reilley.com wrote:
 
 Frank;
 
 Thanks for your long and detailed explanation.
 
 I was able to get the internal OCXO to that precision but it was 
 probably luck
 to get the trimmer that close.   I worked at it for a while.
 
 I am using T.I. mode with the averaging mode.   I assumed that it took 10K
 readings
 and averaged the results.   Is that not correct?   Is something mode
 complicated
 going on?
 
 I will have to set up the GPIB and give that a try.   I did get TimeLab.
 This will be new territory to me.
 
 I did try measuring it's own 10 MHz frequency with 1 sec gate time.   It
 bounces
 around by about +- 4 in the 10th decimal place.
 
 Is my calibration with the rubidium oscillator valid?   Could it be
 that far off?

An old style analog tune Rb could tune a max of 1x10^-8. It's rare to see
them more than 3x10^-9 off. Most are running under 5x10^-10 when received
from the salvage yard. 

The new style digital tuned Rb's have a range limited by their VCXO (if
it's limited at all). They *should* be  3x10^-9 as received from salvage.
They could be much further off.

Since all of these are tunable devices. The only way to be sure of their
accuracy is to calibrate them against something good.

Bob

 
 I will have to ponder this some more.
 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Frank 
 Stellmach
 Sent: Monday, June 15, 2015 5:01 PM
 To: time-nuts@febo.com
 Subject: [time-nuts] My HP 5370B reads 6 nS out!
 
 Pete,
 
 you do not specify, whether you use FREQ or T.I. when you use the 
 averaging function.
 
 First of all, its OCXO can be adjusted to a few parts in 1e-9 only, as 
 the trimmer is too unprecise.
 If the OCXO is running for several weeks already (idle state), its 
 drift may be as low as a few parts in 1e-10 or better.
 
 If you put the instrument to FREQ mode, you may measure and the 10MHz 
 of the GPSDO standard to about 2e-11 resolution, if you use 1sec time 
 base on the 5370B.
 That should work also, if you directly measure 1pps, but you have to 
 properly adjust the trigger level.
 Important: Don't use the 10k statistics, set the 5370A also to 1sec 
 time base!
 Due to this low frequency, jitter should be higher, see specifications.
 
 You better do statistics by means of a PC, over GPIB.
 That will show the 30ps jitter of the 5370B, and the jitter of the 
 GPSDO, on the order of 1e-10.
 
 You may also calibrate the OCXO of the 5370B this way, instead of that 
 oscilloscope method.
 
 I strongly recommend Timelab from John Miles to do these measurements 
 properly.
 http://www.ke5fx.com/timelab/readme.htm
 
 
 If you use the internal 10k statistics 10k, pay attention!!
 
 In this instance, the 5370B will do the frequency measurement in a 
 different manner..
 Not 100% sure, it will be a sort of a T.I. measurement, calculated to 
 frequency.
 And that may produce a constant offset, if the internal T.I. 
 calibration is not done properly.
 Look into the specs, its absolute T.I. uncertainty is 1ns only, 
 although it resolves 20ps.
 
 
 You may check that behaviour

Re: [time-nuts] My HP 5370B reads 6 nS out!

[Peter Reilley]

Bob;

It seems reasonable to calibrate my 5370B using the 1 PPS signal from
my Resolution T and assume that my rubidium oscillator is 6 X 10^-9 off.
There is no reason to believe that the GPS 1 PPS signal is wrong.

The FEI FE-5680A devices seem to be hard to determine what options they
actually have.   Perhaps it just needs calibration.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Tuesday, June 16, 2015 7:02 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] My HP 5370B reads 6 nS out!

Hi
 On Jun 15, 2015, at 9:51 PM, Peter Reilley pe...@reilley.com wrote:
 
 Frank;
 
 Thanks for your long and detailed explanation.
 
 I was able to get the internal OCXO to that precision but it was 
 probably luck
 to get the trimmer that close.   I worked at it for a while.
 
 I am using T.I. mode with the averaging mode.   I assumed that it took 10K
 readings
 and averaged the results.   Is that not correct?   Is something mode
 complicated
 going on?
 
 I will have to set up the GPIB and give that a try.   I did get TimeLab.
 This will be new territory to me.
 
 I did try measuring it's own 10 MHz frequency with 1 sec gate time.   It
 bounces
 around by about +- 4 in the 10th decimal place.
 
 Is my calibration with the rubidium oscillator valid?   Could it be
 that far off?

An old style analog tune Rb could tune a max of 1x10^-8. It's rare to see
them more than 3x10^-9 off. Most are running under 5x10^-10 when received
from the salvage yard. 

The new style digital tuned Rb's have a range limited by their VCXO (if
it's limited at all). They *should* be  3x10^-9 as received from salvage.
They could be much further off.

Since all of these are tunable devices. The only way to be sure of their
accuracy is to calibrate them against something good.

Bob

 
 I will have to ponder this some more.
 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Frank 
 Stellmach
 Sent: Monday, June 15, 2015 5:01 PM
 To: time-nuts@febo.com
 Subject: [time-nuts] My HP 5370B reads 6 nS out!
 
 Pete,
 
 you do not specify, whether you use FREQ or T.I. when you use the 
 averaging function.
 
 First of all, its OCXO can be adjusted to a few parts in 1e-9 only, as 
 the trimmer is too unprecise.
 If the OCXO is running for several weeks already (idle state), its 
 drift may be as low as a few parts in 1e-10 or better.
 
 If you put the instrument to FREQ mode, you may measure and the 10MHz 
 of the GPSDO standard to about 2e-11 resolution, if you use 1sec time 
 base on the 5370B.
 That should work also, if you directly measure 1pps, but you have to 
 properly adjust the trigger level.
 Important: Don't use the 10k statistics, set the 5370A also to 1sec 
 time base!
 Due to this low frequency, jitter should be higher, see specifications.
 
 You better do statistics by means of a PC, over GPIB.
 That will show the 30ps jitter of the 5370B, and the jitter of the 
 GPSDO, on the order of 1e-10.
 
 You may also calibrate the OCXO of the 5370B this way, instead of that 
 oscilloscope method.
 
 I strongly recommend Timelab from John Miles to do these measurements 
 properly.
 http://www.ke5fx.com/timelab/readme.htm
 
 
 If you use the internal 10k statistics 10k, pay attention!!
 
 In this instance, the 5370B will do the frequency measurement in a 
 different manner..
 Not 100% sure, it will be a sort of a T.I. measurement, calculated to 
 frequency.
 And that may produce a constant offset, if the internal T.I. 
 calibration is not done properly.
 Look into the specs, its absolute T.I. uncertainty is 1ns only, 
 although it resolves 20ps.
 
 
 You may check that behaviour, if you apply its own 10Mhz OCXO ouput to 
 the FREQ input, and measure this frequency first on FREQ, 1sec.
 That should give nearly exactly 10MHz,  1e-10 jitter or deviation.
 Mine reads 9.999 999 999 85 MHz, for example.
 
 If you now switch to AVERAGE, SAMPLE SIZE 1, 100, 1k, 10K, you will 
 see, that you will get big deviations as big as 0.1%, although it 
 should measure its own OCXO to precisely 10.0MHZ.
 Mine reads 9,989 294 5 MHz, for example.
 
 That's due to the different measurement method, and should explain 
 6..7ns deviation on the 1pps signal also.
 
 This averaging should only be used with T.I.!
 
 Frank
 
 
 
 
 
 
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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] My HP 5370B reads 6 nS out!

[Peter Reilley]

Frank;

Thanks for your long and detailed explanation.

I was able to get the internal OCXO to that precision but it was probably
luck
to get the trimmer that close.   I worked at it for a while.

I am using T.I. mode with the averaging mode.   I assumed that it took 10K
readings
and averaged the results.   Is that not correct?   Is something mode
complicated
going on?

I will have to set up the GPIB and give that a try.   I did get TimeLab.
This will be new territory to me.

I did try measuring it's own 10 MHz frequency with 1 sec gate time.   It
bounces 
around by about +- 4 in the 10th decimal place.

Is my calibration with the rubidium oscillator valid?   Could it be
that far off?

I will have to ponder this some more.


Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Frank
Stellmach
Sent: Monday, June 15, 2015 5:01 PM
To: time-nuts@febo.com
Subject: [time-nuts] My HP 5370B reads 6 nS out!

Pete,

you do not specify, whether you use FREQ or T.I. when you use the averaging
function.

First of all, its OCXO can be adjusted to a few parts in 1e-9 only, as the
trimmer is too unprecise.
If the OCXO is running for several weeks already (idle state), its drift may
be as low as a few parts in 1e-10 or better.

If you put the instrument to FREQ mode, you may measure and the 10MHz of the
GPSDO standard to about 2e-11 resolution, if you use 1sec time base on the
5370B.
That should work also, if you directly measure 1pps, but you have to
properly adjust the trigger level.
Important: Don't use the 10k statistics, set the 5370A also to 1sec time
base!
Due to this low frequency, jitter should be higher, see specifications.

You better do statistics by means of a PC, over GPIB.
That will show the 30ps jitter of the 5370B, and the jitter of the GPSDO, on
the order of 1e-10.

You may also calibrate the OCXO of the 5370B this way, instead of that
oscilloscope method.

I strongly recommend Timelab from John Miles to do these measurements
properly.
http://www.ke5fx.com/timelab/readme.htm


If you use the internal 10k statistics 10k, pay attention!!

In this instance, the 5370B will do the frequency measurement in a 
different manner..
Not 100% sure, it will be a sort of a T.I. measurement, calculated to 
frequency.
And that may produce a constant offset, if the internal T.I. calibration 
is not done properly.
Look into the specs, its absolute T.I. uncertainty is 1ns only, although 
it resolves 20ps.


You may check that behaviour, if you apply its own 10Mhz OCXO ouput to 
the FREQ input, and measure this frequency first on FREQ, 1sec.
That should give nearly exactly 10MHz,  1e-10 jitter or deviation.
Mine reads 9.999 999 999 85 MHz, for example.

If you now switch to AVERAGE, SAMPLE SIZE 1, 100, 1k, 10K, you will see, 
that you will get big deviations as big as 0.1%, although it should 
measure its own OCXO to precisely 10.0MHZ.
Mine reads 9,989 294 5 MHz, for example.

That's due to the different measurement method, and should explain 
6..7ns deviation on the 1pps signal also.

This averaging should only be used with T.I.!

Frank






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[time-nuts] My HP 5370B reads 6 nS out!

[Peter Reilley]

I just got a new (to me) HP 5370B and I wanted to try it out on the 1 PPS
output
from a Trimble Resolution T.   Using 10K samples averaging it is always
about
6 or 7 nS to high.   Shouldn't this average toward zero?   If I use no
averaging
it bounces around within the expected range.
 
I have done this test using the internal oscillator and an external rubidium
frequency
standard.   I get the about the same results in both cases.
 
I did calibrate the OCXO in the 5370B using the rubidium standard and got it
so
that there is less than one cycle difference between the two over a period
of a few
hours.
 
I have tried a number of GPS units with the same result.
 
Could my rubidium oscillator be that far out?   It is a FEI model FE5680A.
 
Am I missing something?
 
Pete.
 
 
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Re: [time-nuts] Need advice for multilateration setup

[Peter Reilley]

Some crystal oscillators specify their sensitivity to G forces.
Here is one:
http://www.abracon.com/Precisiontiming/AOCJYR-24.576MHz-M6069LF.pdf

Available here:
http://www.digikey.com/product-detail/en/AOCJYR-24.576MHZ-M6069LF/535-12627-
1-ND/4989033

Others specify shock and vibration limits but say nothing about 
frequency stability.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris
Albertson
Sent: Friday, March 27, 2015 9:55 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Need advice for multilateration setup

On Fri, Mar 27, 2015 at 10:29 AM, Chuck Harris cfhar...@erols.com wrote:

 The biggest problem I see is the crystal oscillator in the rocket is 
 going to notice the G forces during acceleration in a pretty big way.


But all of the ground stations will see the same frequency shift on the
rocket's transmitter.   I think this can be backed out in processing.

Someone needs to write the equations and post them here.
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Need advice for multilateration setup

[Peter Reilley]

Robert;

It seems that a Doppler system should work for you.

But first, you have a problem.   If you want to track your rocket
to 100K feet (20 miles) using some form of triangulation then you
need your receiving stations further apart than 1 mile.   Your
triangle is too extreme and any measurement error will be greatly
amplified.

Here is what I suggest.

Place a simple transmitter in the rocket of say 100 MHz.   It 
really should be a legal frequency, 2 meter ham band?   The 
transmitted frequency is not modulated and should be stable
for the duration of the flight.

The receiving stations should have a very narrow receive filter
on the front end and mix the signal with a local oscillator that is
5 KHz off from the rocket frequency.   For example: 100.005 MHz.
A narrow audio filter will help as well.   This is results in a 
very narrow bandwidth receiver which is very good in rejecting 
received noise.

Take the audio signal and feed it into a computer's audio input.
Sample the audio A/D converter as fast as you can and timestamp
each sample.   The computer's clock should be synchronized with
your GPS receiver's time.

This system measures velocity relative to your vantage point.
Because distance is the integral of velocity you can calculate
the distance during your flight.   Since the initial positions
are known you can calculate absolute position.

If we assume a 100 MHz transmitter and with the speed of light
at 300,000 KM/S you will see about 1/3 of a HZ shift for each 1 M/S
of velocity.

You do not need super stable oscillators.   They only need 
to be stable for the duration of the flight.

Here is how the flight will be tracked:

Before the flight, the ground stations will receive the 100 MHz
from the rocket and record the offset between the rocket's
oscillator and the local oscillator.   Any error will show up
as the 5 KHz being somewhat off.   This is not a problem if
it remains constant during the flight. 

Before the flight the computer logs the audio input data
with the timestamp.   This is the reference data.

When the rocket is launched the computer continues logging
but should notice the shift in frequency.   The entire set
of logged data should show the velocity profile for the entire
flight.   This can be converted to distance since all of the
initial positions of the ground stations and the rocket are
known.   Using the data from all the ground stations you can
calculate the absolute position of the rocket for the entire 
flight.

This setup should easily fit within your budget.   The crystal
oscillators do not need to be super precise or stable.
They only need to be stable for the duration of the flight
since the system calibrates itself immediately before launch.

Pete.
 

Robert Watzlavick wrote:
 I'm working on a project that I could use some advice on and also might be
of interest to the list.   If it's not 
 appropriate for the list, my apologies.

 I want to develop a tracking system for an amateur rocket that can 
 allow me to track the rocket even if onboard GPS is lost (as is 
 typical during ascent and sometimes during descent) or if telemetry is
lost.  The idea is to use a transmitter in the rocket and have 4 or more
ground stations about a mile apart each receive the signal.
 Multilateration based on TDOA (time difference of arrival) 
 measurements would then be used to determine x, y, z, and t.  With at 
 least 4 ground stations, you don't need to know the time the pulse was 
 transmitted.  The main problem I'm running into is that most of the 
 algorithms I've come across are very sensitive to the expected 
 uncertainty in the time measurements.  I had thought 100 ns of timing
accuracy in the received signals would be good enough but I think I need to
get down less than 40 ns to keep the algorithms from blowing up.  My desired
position accuracy is around 100 ft up to a range of 100k ft.

 There were two different methods I thought of.  The first method would 
 transmit a pulse from the rocket and then use a counter or TDC on the 
 ground to measure the time difference between a GPS PPS and the pulse 
 arrival.  This is the most straightforward method but I'm worried about
the timing accuracy of the pulse measurement.  I should be able to find a
timing GPS that has a PPS output with about +/- 30-40 ns of jitter (2 sigma)
so that portion is in the ballpark.
 There also seem to be TDCs that have accuracy and resolution in the tens
of picosecond range but they also have a 
 maximum interval in the millisecond range.   I'm not sure I can ensure the
pulse sent from the rocket will be within a 
 few miilliseconds of the 1 PPS value on the ground.  I will have 
 onboard GPS before launch so in theory I could initialize a counter to 
 align the transmit pulse within a millisecond or so to the onboard 
 PPS. But, once GPS is lost on ascent, unless I put an OCXO onboard 
 that pulse may drift too far away (due to temperature, acceleration, 
 etc.) for the TDC on the ground to pick 

Re: [time-nuts] Correcting jitter on the1 PPSsignalfromaGPSreceiver.

[Peter Reilley]

You need not have a properly terminated transmission line but you
must then worry about the bounce.   If you understand the size
of the bounce and have a system that will not suffer false triggering
then you will be OK.   

There are some worries however.  It is hard to predict the exact
size of the bounce since any measurements that you take necessarily
affect the impedance of the line and therefore the characteristics 
of the bounce.

If you change the components of your transmission line then you effect
the size of the bounce.   High quality (low loss) coax will have 
a larger bounce than crappy coax.

The terminating impendence that you do have affects the bounce.
Is the receiving device 1 M ohm?   Is it 1 K ohm.  The capacitance
also has an effect.  Is it 10 pF, 100 pF, 1000 pF?   Complex 
impedances are lots of fun to figure out in these situations.
A 50 Ohm terminator generally swamps any complex impedance effects
and they can generally be ignored,

The length of the coax will effect the size and position of the 
bounce.

Do you know the size of the bounce?   Do you know your system's 
trigger set point?   Can you adjust the set point?

If you use a properly terminated cable these worries mostly go away.
You can run without a termination, it is just easier and more reliable
with it.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike S
Sent: Monday, September 15, 2014 10:29 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Correcting jitter on the1
PPSsignalfromaGPSreceiver.

On 9/15/2014 10:01 AM, Tom Miller wrote:
 Fast risetime pulses _are_ RF and need to be treated as such.

You say that as if simply saying it provides an explanation, or even a
reason. Exactly what ill effect on a triggered measurement is there if one
does not terminate a PPS signal properly? Does/can termination increase the
slew rate or make the speed of propagation more consistent, which might make
the measurement more accurate?

Like Tom said, what comes after the leading edge of a PPS signal (which is
the measurement trigger) seems irrelevant.

A simple though experiment. If I take a high impedance measurement at a tap
1M from the source, and the cable ends another 100M away, how can the
termination or lack thereof at that end effect my measurement of a single
event? It's over 700 ns round trip away? If I repeat that event 1/sec, is it
any different? I can see where there would be a difference when I get close
to a 700 ns cycle time, and likely before because of ringing. But for a 1
second cycle? Someone will have to provide more than a dismissive just
because to convince me.
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Re: [time-nuts] Correcting jitter on the 1 PPS signal from aGPSreceiver.

[Peter Reilley]

I don't see any mention of sawtooth correction in their documentation.
I take that to imply that sawtooth correction is not necessary to get 
the 15 nS that is spec'ed?

Does the 15 nS imply that the internal clock is 33 MHz?   That is: +-15 nS
is 30 nS which is 33 MHz.   Is that correct?  Or do they need a higher
internal
clock so that all errors sum to less than 15 nS? 

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Saturday, September 13, 2014 8:03 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from
aGPSreceiver.

Hi

I'm sure they expect you to take out the sawtooth error before you do the
comparison. Are you doing that?

Bob

On Sep 13, 2014, at 6:41 PM, Peter Reilley pe...@reilley.com wrote:

 I see in the Trimble Resolution T data sheet that they say that the 
 PPS signal is within 15 nS to GPS or UTC (1 Sigma) when using an over 
 determined solution in stationary mode..
 I take this to mean that the PPS signal should be within 15 nS and 
 that comparing 2 units that there should be no more than
 30 nS between the two edges.   This is comparing the rising edges.
 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
 Camp
 Sent: Saturday, September 13, 2014 6:26 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from a 
 GPSreceiver.
 
 Hi
 
 Where are you getting the 15 ns accuracy number from? When I look at 
 the Trimble spec's they have a number of errors described (like 
 sawtooth) that are larger than 15 ns.
 
 Bob
 
 On Sep 13, 2014, at 10:41 AM, Peter Reilley pe...@reilley.com wrote:
 
 I have 2 Trimble Resolution T receivers and I have compared the 1 PPS
 signal
 between the 2 units.   They are spec'ed at 15 nS accuracy.I am seeing
 about
 80 nS of jitter between the two.   This is with about 6 satellites in
 view.
 
 I was thinking about ways to improve this.   Since this is a stationary
 installation,
 can you use the jitter in the reported location (latitude and
 longitude) to correct for the 1 PPS jitter?
 
 The location data is derived using the internal GPS disciplined 
 oscillator so both
 pieces of information should show the same jitter error.   If you compare
 the reported
 location with the known fixed location you should be able to use that 
 error to correct for the 1 PPS error.
 
 Does this make sense or am I missing something?
 
 Pete.
 
 
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Re: [time-nuts] Correcting jitter on the 1 PPS signal fromaGPSreceiver.

[Peter Reilley]

My rise time is about 4 nS.   I am measuring that with my 200 MHz
scope.   I am only using 50 Ohm termination, anything else is not
valid when using 50 Ohm coax. 

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Saturday, September 13, 2014 10:34 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal
fromaGPSreceiver.

 The cables are not exactly the same lengths.   Differences in length
 will result in a fixed offset.   I am not concerned about such fixed
 errors, only jitter.
 
 I am comparing the rising edges which is what the spec defines as the 
 reference edge.
 
 Pete.

Pete,

Correct, the survey position is determined only by the phase center of the
antenna, not by cable length. And cable length mismatches should make no
difference in your jitter measurements.

But one thing to check is how sharp the 1PPS rising edge is -- right at the
input to your TI counter. I use a BNC tee with one leg open allowing a
'scope check (set to 1M input). If your risetime is a couple of ns like mine
is, then all is well. Slow risetime can be a huge source of timing jitter.
Check both 50R and 1M at the counter input. Use DC, not AC coupling. Use
fixed trigger, never auto-trigger. Pick a trigger level that matches the
maximum slope.

Some examples of good/bad GPS 1PPS risetimes:
http://leapsecond.com/pages/gpsdo-rise/

/tvb


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Re: [time-nuts] Correcting jitter on the 1 PPS signalfromaGPSreceiver.

[Peter Reilley]

I tried removing the termination and got a little better than 4 nS
risetime.

Isn't the ringing frequency simply a function of the length of
the coax?   Isn't it the price you pay for mismatched impedances?

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Said
Jackson via time-nuts
Sent: Sunday, September 14, 2014 11:43 AM
To: Said Jackson; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS
signalfromaGPSreceiver.

Ok, did the math, a 4ns risetime should be ok on a 200MHz scope.

You likely won't see the oscillations and reflections visible in Toms 58503A
plots for example, they are faster than the risetime.

Bye,
Said

Sent From iPhone

 On Sep 14, 2014, at 8:35, Said Jackson via time-nuts time-nuts@febo.com
wrote:
 
 Peter,
 
 You don't need nor do you want a 50 ohms end-termination on a
series-terminated 50 ohms coax cable.
 
 This has been discussed here extensively before, please check the
archives. Your last sentence is not correct.
 
 Also, you are running into your scope's BW limit if you are measuring a
4ns risetime with a 200MHz scope..
 
 Bye,
 Said
 
 Sent From iPhone
 
 On Sep 14, 2014, at 6:19, Peter Reilley pe...@reilley.com wrote:
 
 My rise time is about 4 nS.   I am measuring that with my 200 MHz
 scope.   I am only using 50 Ohm termination, anything else is not
 valid when using 50 Ohm coax. 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom 
 Van Baak
 Sent: Saturday, September 13, 2014 10:34 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal 
 fromaGPSreceiver.
 
 The cables are not exactly the same lengths.   Differences in length
 will result in a fixed offset.   I am not concerned about such fixed
 errors, only jitter.
 
 I am comparing the rising edges which is what the spec defines as 
 the reference edge.
 
 Pete.
 
 Pete,
 
 Correct, the survey position is determined only by the phase center 
 of the antenna, not by cable length. And cable length mismatches 
 should make no difference in your jitter measurements.
 
 But one thing to check is how sharp the 1PPS rising edge is -- right 
 at the input to your TI counter. I use a BNC tee with one leg open 
 allowing a 'scope check (set to 1M input). If your risetime is a 
 couple of ns like mine is, then all is well. Slow risetime can be a huge
source of timing jitter.
 Check both 50R and 1M at the counter input. Use DC, not AC coupling. 
 Use fixed trigger, never auto-trigger. Pick a trigger level that 
 matches the maximum slope.
 
 Some examples of good/bad GPS 1PPS risetimes:
 http://leapsecond.com/pages/gpsdo-rise/
 
 /tvb
 
 
 ___
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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 and follow the instructions there.
 
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Re: [time-nuts] Correcting jitter on the 1 PPS signalfromaGPSreceiver.

[Peter Reilley]

Thank you for that link.   I read the section of quantization error.
I am confused with what I am seeing on my scope verses what they are saying

They say that the system clock is 12.504 MHz and that they use both the
rising and falling edges.   That is about 40 nS between quantization time
slots.   The PPS can only appear on a 40 nS edge.   I should be seeing 
40 nS jumps in the waveforms.   I do see ~40 nS jumps but they are less 
common.

The waveform timing is clearly quantized but I am seeing ~2 nS jumps.
My scope is a Rigol DS2202 which samples at 1 GSP in 2 channel mode.
Could this 2 nS quantization be a result of the scope?   Perhaps I should
get my 400 MHz analog scope out (Tek 2465B) and repeat the measurements?

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Sunday, September 14, 2014 11:30 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS
signalfromaGPSreceiver.

Hi

If you look at:

ftp://ftp.trimble.com/pub/sct/embedded/bin/Manuals/Old%20Manuals/Resolution%
20T%20Final%20Final.pdf

(first hit on Google for Resolution T manual, no other reason for picking
it).

In the index, PPS Quantization Error is on page 46.

On page 46 they talk about the +/- 20 ns error from sawtooth and how to
correct it out.

Page 47 shows the plot with the sawtooth still in the signal. Page 48 shows
the plot with it removed.

Bob



On Sep 14, 2014, at 9:19 AM, Peter Reilley pe...@reilley.com wrote:

 My rise time is about 4 nS.   I am measuring that with my 200 MHz
 scope.   I am only using 50 Ohm termination, anything else is not
 valid when using 50 Ohm coax. 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom 
 Van Baak
 Sent: Saturday, September 13, 2014 10:34 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal 
 fromaGPSreceiver.
 
 The cables are not exactly the same lengths.   Differences in length
 will result in a fixed offset.   I am not concerned about such fixed
 errors, only jitter.
 
 I am comparing the rising edges which is what the spec defines as the 
 reference edge.
 
 Pete.
 
 Pete,
 
 Correct, the survey position is determined only by the phase center of 
 the antenna, not by cable length. And cable length mismatches should 
 make no difference in your jitter measurements.
 
 But one thing to check is how sharp the 1PPS rising edge is -- right 
 at the input to your TI counter. I use a BNC tee with one leg open 
 allowing a 'scope check (set to 1M input). If your risetime is a 
 couple of ns like mine is, then all is well. Slow risetime can be a huge
source of timing jitter.
 Check both 50R and 1M at the counter input. Use DC, not AC coupling. 
 Use fixed trigger, never auto-trigger. Pick a trigger level that 
 matches the maximum slope.
 
 Some examples of good/bad GPS 1PPS risetimes:
 http://leapsecond.com/pages/gpsdo-rise/
 
 /tvb
 
 
 ___
 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] Correcting jitter on the 1 PPS signalfromaGPSreceiver.

[Peter Reilley]

I don't want to repeat an old discussion.   You certainly can
use unterminated coax as long as you are aware of the ringing
issues and the possibility of false triggering.

I am using a terminator on the scope end of the cable.   I can
see ringing similar to what is shown on the leapsecond web site
when I don't terminate.   With termination the waveforms are
also similar so I am comfortable that my cables and terminators
are working as they should.   My scope does not have a built-in
terminator.

Is there a good way of searching the archives? 

My scope is a Rigol DS2202 200 MHz scope that samples at 1 GSP
in two channel mode.  I understand the problems that you can run
into as you approach the sampling limits of digital scopes.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Said
Jackson via time-nuts
Sent: Sunday, September 14, 2014 11:36 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS
signalfromaGPSreceiver.

Peter,

You don't need nor do you want a 50 ohms end-termination on a
series-terminated 50 ohms coax cable.

This has been discussed here extensively before, please check the archives.
Your last sentence is not correct.

Also, you are running into your scope's BW limit if you are measuring a 4ns
risetime with a 200MHz scope..

Bye,
Said

Sent From iPhone

 On Sep 14, 2014, at 6:19, Peter Reilley pe...@reilley.com wrote:
 
 My rise time is about 4 nS.   I am measuring that with my 200 MHz
 scope.   I am only using 50 Ohm termination, anything else is not
 valid when using 50 Ohm coax. 
 
 Pete.
 
 
 -Original Message-
 From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom 
 Van Baak
 Sent: Saturday, September 13, 2014 10:34 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal 
 fromaGPSreceiver.
 
 The cables are not exactly the same lengths.   Differences in length
 will result in a fixed offset.   I am not concerned about such fixed
 errors, only jitter.
 
 I am comparing the rising edges which is what the spec defines as the 
 reference edge.
 
 Pete.
 
 Pete,
 
 Correct, the survey position is determined only by the phase center of 
 the antenna, not by cable length. And cable length mismatches should 
 make no difference in your jitter measurements.
 
 But one thing to check is how sharp the 1PPS rising edge is -- right 
 at the input to your TI counter. I use a BNC tee with one leg open 
 allowing a 'scope check (set to 1M input). If your risetime is a 
 couple of ns like mine is, then all is well. Slow risetime can be a huge
source of timing jitter.
 Check both 50R and 1M at the counter input. Use DC, not AC coupling. 
 Use fixed trigger, never auto-trigger. Pick a trigger level that 
 matches the maximum slope.
 
 Some examples of good/bad GPS 1PPS risetimes:
 http://leapsecond.com/pages/gpsdo-rise/
 
 /tvb
 
 
 ___
 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] Correcting jitter on the 1PPSsignalfromaGPSreceiver.

[Peter Reilley]

I am beginning to understand the complexity of these issues
thanks to everyone's help. 

Thanks,
Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Sunday, September 14, 2014 2:06 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the
1PPSsignalfromaGPSreceiver.

 They say that the system clock is 12.504 MHz and that they use both the
 rising and falling edges.   That is about 40 nS between quantization time
 slots.   The PPS can only appear on a 40 nS edge.   I should be seeing 
 40 nS jumps in the waveforms.   I do see ~40 nS jumps but they are less 
 common.

The PPS can only appear on a 40 ns edge -- of the imprecise, unstable,
uncompensated, unshielded, crystal oscillator on the Resolution-T board. It
may be 12.504 MHz, but it certainly isn't (and not intended to be)
12.50400 MHz. There's also instability in your 'scope or counter. Thus
you will see significant jitter, drift, and wander in the observed 40 ns
edges. All this is normal and expected any time you beat two oscillators
against each other.

The net result is that the jumps are very evenly (and not Gaussian)
distributed anywhere from 0 ns to 40 ns. Again, look at the raw data, plots,
and histograms that I provided. Especially the zebra plots which show just
how varied the sawtooth error is over the span of minutes, hours, and days:

http://leapsecond.com/pages/MG1613S/tic-72-hour.gif (3600x1800 pixels!)

 The waveform timing is clearly quantized but I am seeing ~2 nS jumps.
 My scope is a Rigol DS2202 which samples at 1 GSP in 2 channel mode.
 Could this 2 nS quantization be a result of the scope?   Perhaps I should
 get my 400 MHz analog scope out (Tek 2465B) and repeat the measurements?

Off-list you mentioned you don't have a ns or sub-ns time interval counter,
so yes, I guess you should try the analog 'scope. I'm wondering now if your
GPS receiver more stable than your scope's timebase.

/tvb

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[time-nuts] Correcting jitter on the 1 PPS signal from a GPS receiver.

[Peter Reilley]

I have 2 Trimble Resolution T receivers and I have compared the 1 PPS signal
between the 2 units.   They are spec'ed at 15 nS accuracy.I am seeing
about
80 nS of jitter between the two.   This is with about 6 satellites in view.
 
I was thinking about ways to improve this.   Since this is a stationary
installation,
can you use the jitter in the reported location (latitude and longitude) to
correct
for the 1 PPS jitter?
 
The location data is derived using the internal GPS disciplined oscillator
so both
pieces of information should show the same jitter error.   If you compare
the reported
location with the known fixed location you should be able to use that error
to correct
for the 1 PPS error.
 
Does this make sense or am I missing something?
 
Pete.
 
 
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Re: [time-nuts] Correcting jitter on the 1 PPS signal from a GPSreceiver.

[Peter Reilley]

Yes, both have completed their surveys.   During the survey process
I was getting up to 150 uS of error between the PPS pulses. 

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Saturday, September 13, 2014 4:33 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from a
GPSreceiver.

Hi

Have they both completed a survey and does the survey make sense?

Bob

On Sep 13, 2014, at 10:41 AM, Peter Reilley pe...@reilley.com wrote:

 I have 2 Trimble Resolution T receivers and I have compared the 1 PPS
signal
 between the 2 units.   They are spec'ed at 15 nS accuracy.I am seeing
 about
 80 nS of jitter between the two.   This is with about 6 satellites in
view.
 
 I was thinking about ways to improve this.   Since this is a stationary
 installation,
 can you use the jitter in the reported location (latitude and 
 longitude) to correct for the 1 PPS jitter?
 
 The location data is derived using the internal GPS disciplined 
 oscillator so both
 pieces of information should show the same jitter error.   If you compare
 the reported
 location with the known fixed location you should be able to use that 
 error to correct for the 1 PPS error.
 
 Does this make sense or am I missing something?
 
 Pete.
 
 
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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Correcting jitter on the 1 PPS signal from a GPSreceiver.

[Peter Reilley]

I see in the Trimble Resolution T data sheet that they
say that the PPS signal is within 15 nS to GPS or UTC (1 Sigma) 
when using an over determined solution in stationary mode..
I take this to mean that the PPS signal should be within 15 nS
and that comparing 2 units that there should be no more than 
30 nS between the two edges.   This is comparing the rising edges.


Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Saturday, September 13, 2014 6:26 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from a
GPSreceiver.

Hi

Where are you getting the 15 ns accuracy number from? When I look at the
Trimble spec's they have a number of errors described (like sawtooth) that
are larger than 15 ns.

Bob

On Sep 13, 2014, at 10:41 AM, Peter Reilley pe...@reilley.com wrote:

 I have 2 Trimble Resolution T receivers and I have compared the 1 PPS
signal
 between the 2 units.   They are spec'ed at 15 nS accuracy.I am seeing
 about
 80 nS of jitter between the two.   This is with about 6 satellites in
view.
 
 I was thinking about ways to improve this.   Since this is a stationary
 installation,
 can you use the jitter in the reported location (latitude and 
 longitude) to correct for the 1 PPS jitter?
 
 The location data is derived using the internal GPS disciplined 
 oscillator so both
 pieces of information should show the same jitter error.   If you compare
 the reported
 location with the known fixed location you should be able to use that 
 error to correct for the 1 PPS error.
 
 Does this make sense or am I missing something?
 
 Pete.
 
 
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Re: [time-nuts] Correcting jitter on the 1 PPS signal from a GPSreceiver.

[Peter Reilley]

The cables are not exactly the same lengths.   Differences in length
will result in a fixed offset.   I am not concerned about such fixed
errors, only jitter.

I am comparing the rising edges which is what the spec defines as the 
reference edge.

Pete.
 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris
Albertson
Sent: Saturday, September 13, 2014 6:12 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from a
GPSreceiver.

On Sat, Sep 13, 2014 at 1:33 PM, Bob Camp kb...@n1k.org wrote:

 Hi

 Have they both completed a survey and does the survey make sense?


Are all of the cables the same length?  That includes the cables from
antenna to receiver and the cable carrying the 1PPS from the receiver to
where you are measuring.

And also are you SURE you are measuring the correct end of the pulse, you
want the raising edge.  It is easy to invert the pulse and therefore measure
the falling edge.


Chris Albertson
Redondo Beach, California
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