Re: [time-nuts] Moving GPSDO

[Keith Loiselle]

Hal Murray wrote:



I think Jackson Labs makes some non-survey GPSDOs.

http://www.jackson-labs.com/index.php/products/lte_lite

The FAQ says there is a non-survey mode.



You might find something interesting in time-nuts archives from about 2 years

ago.


Here are some comments we put together regarding mobile GPSDO's:


Using GPSDOs in mobile applications is a fascinating and very complex
topic. There are three main issues affecting 3D mobile mode performance: 1)
the oscillator sensitivity to acceleration, 2) the GNSS receiver
sensitivities, and Kalman time-constants wrt motion and multipath, and its
performance difference in 3D versus Position Hold mode, 3) the products’
sensitivity to possible airflow or temperature changes during motion (for
example when operated in a UAV that has no airflow shielding).



Jackson Labs Technologies, Inc. indeed makes a large number of
mobile-capable GPSDO’s, some with vibration- and acceleration-hardened
oscillators. This typically involves hardening of the crystal mounts and
low-g sensitivity operation, and/or some sort of electronic g-compensation,
and proper “steering” of the GPS receivers’ Kalman filter modes (time
constants) and Doppler versus Carrier Phase tracking modes, but all of this
depends on what “mobile” really means, e.g. what type of dynamics can be
expected. There is a huge difference in expected operation between walking
and a jet pulling 5g maneuvers.



In our GPSDO’s and GNSS receivers starting with the low-cost $220 M12M
Replacement Receiver the Kalman and tracking mode can be auto-set and
auto-sensed via the GPS:DYMANIC command. The software will recognize
acceleration, velocity, and change of altitude and set the GPS receiver to
the proper mode that is optimal for a particular environment. There is a
huge difference between operating while walking, or the aircraft is taxiing
on the ground and getting all this multipath from the angled adjacent
hangar roofs, versus what needs to happen once the aircraft is 200+ feet
off the ground for example.



In terms of sensitivity to acceleration, and GPS performance while in
motion, we continuously do flight testing as well as drive testing and have
found that the modern GPS receivers are not very sensitive at all to
high-velocity airborne operation. Driving on freeways does present
challenges due to overpass shading, as well as multipath caused by highway
signs passing by. Usually this is not an issue because modern receivers are
able to track such a large number of satellites. Also, it is impressive to
see how quickly the modern GNSS receivers recover from their TCXO’s being
accelerated in aerobatic flight for example.



GPSDO Oscillator sensitivity to acceleration depends on the type of crystal
used. TCXO’s typically have the highest g-sensitivity (2 to 3ppb or more
per g per axis), while SC-cut DOCXOs we use have sensitivities of 1 to
1.5ppb per g typically, and low-g ordering options have less to much less
than 0.3ppb per g per axis sensitivity. During our flight testing in jets
and propeller aircraft for example we found that our “standard” DOCXOs as
used on the Fury DOCXO and other products exhibit negligible effects on
frequency stability and timing stability even when flying acrobatics (zero
g, 2g steep turns, etc). These maneuvers are typically short (less than 30
seconds) and the phase/frequency deviation experienced does not cause a lot
of drift, and once you pull out of the maneuver the crystal will go back to
its nominal frequency. These events are also short enough typically that
they fall well within the time constant of the loop filter, so the filter
does not “chase” the frequency offset. Thermal and airflow sensitivity
seems to be much more of an issue for TCXO’s and single-oven oscillators
than acceleration sensitivity during driving/flying, while warmup and
retrace errors seem to trump the g-sensitivity in DOCXO products in
airborne applications.


However if you are talking about dismounted applications (someone walking
and wearing a unit in a back pack etc) it is a totally different ballgame
because this backpack could be set onto the ground and turn over, the
person could be walking or lying down, etc etc. The change of direction for
dismounted use is much higher than for vehicle or aircraft use (if a
vehicle turns upside down you are in big trouble anyways, and aircraft
usually fly coordinated meaning the highest acceleration is always down the
z-axis. This allows users to mount the GPSDO in the aircraft with the
lowest crystal g-sensitivity pointing toward the z-axis to minimize
errors). Thus for accurate operation in these types of applications usually
low-g-sensitivity oscillators are used (less than 0.3ppb per g). Vibration
due to turbulence etc is nominally sinusoidal and thus will only cause
phase noise and short-term perturbations that average out over time.



Rubidium and Cesium oscillators have the best g-sensitivity specs, in fact
the Microsemi Rb’s and Cs’ we 

Re: [time-nuts] Moving GPSDO

[Attila Kinali]

On Mon, 17 Oct 2016 16:44:55 +0200
Attila Kinali  wrote:

> 3) Rb vapor standards have very low acceleration effects. As Dave
> said, the control loop will kill most of the effects inside the
> loop frequency. The loop frequency is relatively fast, in the
> order of couple of 100Hz to a couple of 10kHz, depending on the
> exact build of the Rb standard and what type of crystal they used.
> Contrary to what he says, there are no acceleration dependent
> diffusion effects. The vapor cell is is heated and the gas atoms
> in there are pretty fast, any acceleration of them will be negligible
> compared to what they do upon collision. The relativistic red shift due
> to acceleration is way too low to measure (much lower than the intrinsic 
> noise). The only mechanical effect that is possible, is bending of
> the microwave cavity or the parts inside. But given that the cavity
> is several mm thick aluminium and everything is mounted rigidly,
> I very much doubt that there is any significant effect.


Correction: I just had a look at the LPRFS specs. It lists a 2g tip-over
sensitivity of 2*10^-10/g on the worst axis. I have no idea what's going
on there. No other of the Rb vapor standards of which I have the spec
at hand list any acceleration sensitivity.


Attila Kinali

-- 
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the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] Moving GPSDO

[Mark Sims]

A lot of the telecom GPSDOs that speak SCPI have no way of running except in a 
"position hold" mode.   The Trimble Thunderbolt and telecom GPSDOs (like the 
NTBW, NTPX, etc) units can run in a dynamic environment... how well they do 
that is left as an exercise for the user to determine.  They also have commands 
for specifying the movement environment to expect.

All the GPS timing receivers that I have can work in either a dynamic or fixed 
position mode.  Most also have a way of specifying the movement environment / 
dynamics.

> In addition to TimeNuts, there are actually *are* people who get nutty about 
> measuring 
changes in gravity.

Hey!   I resemble that remark!  I have a Worden gravity meter around here... 
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Re: [time-nuts] Moving GPSDO

[Bob Camp]

Hi

Survey is pretty much a bad thing while in motion :)

Some (but not all) GPS modules allow you to set up in a “mobile / do not 
survey” mode. This is one area that the 
newer ( = not 1997 era) devices do much better at. It also is something that 
SBAS / EGNOS / WAAS may indeed
help you out on. You may be changing *many* settings on the part to make it 
behave in a mobile setting. There
are a few bugs you just may turn up while doing this ….

Bob


> On Oct 17, 2016, at 1:38 PM, Nick Sayer via time-nuts  
> wrote:
> 
> Speaking for my GPSDOs specifically, you can’t disable the survey mode with 
> the Venus838 receiver (well, you can, but it requires you to talk to the 
> module with SkyTraq’s software, which requires disabling the GPSDO’s 
> controller - possible to do, but annoying). I haven’t attempted to see what 
> it would do if it were moved after the survey is completed (if you move 
> during the survey, then the survey will fail and repeat).
> 
> The older GPSDOs that had PA6H receivers were navigation receivers that 
> didn’t have a survey mode.
> 
> In either case, without a surveyed position, PPS stability will suffer 
> if/when the constellation degrades due to poor reception, which can happen 
> if, say, the unit is in a moving vehicle in interesting terrain. Poor PPS 
> stability will have an impact on the PLL, obviously.
> 
>> On Oct 16, 2016, at 9:19 PM, Joseph Gray  wrote:
>> 
>> I'm curious to know how accurately a GPSDO will keep its 10 MHz output
>> while moving. No initial survey to set a position would be done. I
>> don't care about the UTC time.
>> 
>> Joe Gray
>> W5JG
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Re: [time-nuts] Moving GPSDO

[Nick Sayer via time-nuts]

Speaking for my GPSDOs specifically, you can’t disable the survey mode with the 
Venus838 receiver (well, you can, but it requires you to talk to the module 
with SkyTraq’s software, which requires disabling the GPSDO’s controller - 
possible to do, but annoying). I haven’t attempted to see what it would do if 
it were moved after the survey is completed (if you move during the survey, 
then the survey will fail and repeat).

The older GPSDOs that had PA6H receivers were navigation receivers that didn’t 
have a survey mode.

In either case, without a surveyed position, PPS stability will suffer if/when 
the constellation degrades due to poor reception, which can happen if, say, the 
unit is in a moving vehicle in interesting terrain. Poor PPS stability will 
have an impact on the PLL, obviously.

> On Oct 16, 2016, at 9:19 PM, Joseph Gray  wrote:
> 
> I'm curious to know how accurately a GPSDO will keep its 10 MHz output
> while moving. No initial survey to set a position would be done. I
> don't care about the UTC time.
> 
> Joe Gray
> W5JG
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Re: [time-nuts] Moving GPSDO

[Attila Kinali]

On Mon, 17 Oct 2016 07:25:34 -0600
"Cube Central"  wrote:

> I had run across this just yesterday:  
> https://www.youtube.com/watch?v=zILwgQhjC_Q
> 
> He talks about how crystal oscillators are sensitive to movement and changes 
> in gravity.  An interesting watch!

As usual with EEVblog, there are several things wrong with what he presents.

1) As Bob wrote, the acceleration sensitivity of crystals vary a lot more
than the rough number Dave gave.

2) The acceleration sensitivity has very little to do with the cut.
Even though there is some cut related effect on acceleration, it is
very very small. The by far most dominant effect comes from the
mechanical stress of the holder onto the crystal. It is probably
obvious that the crystal and the holders bend upon acceleration.
This bending will cause the crystal to change its frequency due
to stress on the lattice. Now, why are AT cuts worse than SC cuts?
The reason is simple, SC cuts are usually ment for high stability
applications and people tend to take more care with the mounting
and the crystal shape, than for regular AT cuts.

3) Rb vapor standards have very low acceleration effects. As Dave
said, the control loop will kill most of the effects inside the
loop frequency. The loop frequency is relatively fast, in the
order of couple of 100Hz to a couple of 10kHz, depending on the
exact build of the Rb standard and what type of crystal they used.
Contrary to what he says, there are no acceleration dependent
diffusion effects. The vapor cell is is heated and the gas atoms
in there are pretty fast, any acceleration of them will be negligible
compared to what they do upon collision. The relativistic red shift due
to acceleration is way too low to measure (much lower than the intrinsic 
noise). The only mechanical effect that is possible, is bending of
the microwave cavity or the parts inside. But given that the cavity
is several mm thick aluminium and everything is mounted rigidly,
I very much doubt that there is any significant effect.

4) If you think that the tilting your frequency counter will have
a significant effect, you are severly underestimating temperature
and aging effects. Just in comparison, a good SC cut DOCXO has an
aging of a few parts in 10^-9. So each week will affect on your crystal
more than a 1g of acceleration. And that's with a slow aging DOCXO.
Temperature effects are in the order of 1x10^-10/°C to 1x10^-7/°C.
So depending on how good the OCXO is, a single degree of temperature
will cause a larger shift than 1g of acceleration. Etc.pp.


Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Moving GPSDO

[Bob Camp]

Hi

In addition to TimeNuts, there are actually *are* people who get nutty about 
measuring 
changes in gravity. That’s a bit different than what he’s talking about in the 
video. Local
variations in the earth’s mass cause variations in gravity (think mountains or 
similar…). 
They also are one of the things that cause GPS orbits to be “bumpy” rather than 
the nice
smooth curves we tend to think of them as being. 

Bob


> On Oct 17, 2016, at 9:25 AM, Cube Central <cubecent...@gmail.com> wrote:
> 
> I had run across this just yesterday:  
> https://www.youtube.com/watch?v=zILwgQhjC_Q
> 
> He talks about how crystal oscillators are sensitive to movement and changes 
> in gravity.  An interesting watch!
> 
>   -Randal
>   (at CubeCentral)
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
> Sent: Monday, 17 October, 2016 05:48
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
> Subject: Re: [time-nuts] Moving GPSDO
> 
> Hi
> 
> Is the OCXO in your GPSDO acceleration compensated? If not then the 
> acceleration involved in your “moving around” will get into the OCXO at 
> around 1x10^-9 / g. Some OCXO’s are compensated to the 1x10^-11 / g level. 
> Some low cost crystals are up around 2x10^-8. Often vibration is an issue as 
> well, since it is an acceleration, the same stuff applies. 
> 
> How well temperature controlled is your moving environment? Your oscillator 
> can have all sorts of temperature coefficients,. It will respond to dynamic 
> change as well as static change. The sensitivity can be just about anything 
> over the 1x10^-12 / C up to 1x10^-7 / C depending on the part. 
> 
> None of that has anything at all to do with GPS, all of it is something the 
> GPSDO will have to deal with in addition to any GPS errors. Unless you want a 
> very coarse output
> (1x10^-9 to 2x10^-8 / second) you will need some sort of loop filter. If it 
> is in the traditional 
>> 200 seconds range, the stuff above can become very apparent in the 
>> output.  The loop
> does not eliminate error at the (say) 200 seconds point, it only gets going 
> by then. 
> 
> Does your moving around include tunnels? If so, how long will you be in a 
> tunnel? Urban canyons also count in this respect. Once you go down to < 3 
> sats, you are in big trouble for timing in motion. Even with 3, your fix and 
> time performance is degraded. Chugging in and out of holdover has it’s 
> impact. 
> 
> Do you want to use multiple systems? If you are running a mixed mode system, 
> you can go from 100% GPS to 100% GLONASS to 100% BEID0U due to viewing angle. 
>  That tosses a whole *bunch* of issues into the mix. 
> 
> How fast are you going? Moving around can involve move 100’, stop and wait 
> for a day or it can involve something moving at mach 3. By far the most 
> common for a GPSDO is some sort of car, truck, or military vehicle on the 
> highway. There are many other possibilities.  
> 
> Lots of variables. Lots of things to get into the mix in addition to the 
> basic nav math.
> 
> Bob
> 
> 
>> On Oct 17, 2016, at 12:19 AM, Joseph Gray <jg...@zianet.com> wrote:
>> 
>> I'm curious to know how accurately a GPSDO will keep its 10 MHz output 
>> while moving. No initial survey to set a position would be done. I 
>> don't care about the UTC time.
>> 
>> Joe Gray
>> W5JG
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Re: [time-nuts] Moving GPSDO

[Cube Central]

I had run across this just yesterday:  
https://www.youtube.com/watch?v=zILwgQhjC_Q

He talks about how crystal oscillators are sensitive to movement and changes in 
gravity.  An interesting watch!

-Randal
(at CubeCentral)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Monday, 17 October, 2016 05:48
To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
Subject: Re: [time-nuts] Moving GPSDO

Hi

Is the OCXO in your GPSDO acceleration compensated? If not then the 
acceleration involved in your “moving around” will get into the OCXO at around 
1x10^-9 / g. Some OCXO’s are compensated to the 1x10^-11 / g level. Some low 
cost crystals are up around 2x10^-8. Often vibration is an issue as well, since 
it is an acceleration, the same stuff applies. 

How well temperature controlled is your moving environment? Your oscillator can 
have all sorts of temperature coefficients,. It will respond to dynamic change 
as well as static change. The sensitivity can be just about anything over the 
1x10^-12 / C up to 1x10^-7 / C depending on the part. 

None of that has anything at all to do with GPS, all of it is something the 
GPSDO will have to deal with in addition to any GPS errors. Unless you want a 
very coarse output
(1x10^-9 to 2x10^-8 / second) you will need some sort of loop filter. If it is 
in the traditional 
> 200 seconds range, the stuff above can become very apparent in the 
> output.  The loop
does not eliminate error at the (say) 200 seconds point, it only gets going by 
then. 

Does your moving around include tunnels? If so, how long will you be in a 
tunnel? Urban canyons also count in this respect. Once you go down to < 3 sats, 
you are in big trouble for timing in motion. Even with 3, your fix and time 
performance is degraded. Chugging in and out of holdover has it’s impact. 

Do you want to use multiple systems? If you are running a mixed mode system, 
you can go from 100% GPS to 100% GLONASS to 100% BEID0U due to viewing angle.  
That tosses a whole *bunch* of issues into the mix. 

How fast are you going? Moving around can involve move 100’, stop and wait for 
a day or it can involve something moving at mach 3. By far the most common for 
a GPSDO is some sort of car, truck, or military vehicle on the highway. There 
are many other possibilities.  

Lots of variables. Lots of things to get into the mix in addition to the basic 
nav math.

Bob


> On Oct 17, 2016, at 12:19 AM, Joseph Gray <jg...@zianet.com> wrote:
> 
> I'm curious to know how accurately a GPSDO will keep its 10 MHz output 
> while moving. No initial survey to set a position would be done. I 
> don't care about the UTC time.
> 
> Joe Gray
> W5JG
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> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Moving GPSDO

[Bob Camp]

Hi

Is the OCXO in your GPSDO acceleration compensated? If not then the acceleration
involved in your “moving around” will get into the OCXO at around 1x10^-9 / g. 
Some
OCXO’s are compensated to the 1x10^-11 / g level. Some low cost crystals are up
around 2x10^-8. Often vibration is an issue as well, since it is an 
acceleration, the same
stuff applies. 

How well temperature controlled is your moving environment? Your oscillator can 
have
all sorts of temperature coefficients,. It will respond to dynamic change as 
well as static
change. The sensitivity can be just about anything over the 1x10^-12 / C up to 
1x10^-7 / C 
depending on the part. 

None of that has anything at all to do with GPS, all of it is something the 
GPSDO will 
have to deal with in addition to any GPS errors. Unless you want a very coarse 
output 
(1x10^-9 to 2x10^-8 / second) you will need some sort of loop filter. If it is 
in the traditional 
> 200 seconds range, the stuff above can become very apparent in the output.  
> The loop
does not eliminate error at the (say) 200 seconds point, it only gets going by 
then. 

Does your moving around include tunnels? If so, how long will you be in a 
tunnel? Urban
canyons also count in this respect. Once you go down to < 3 sats, you are in 
big trouble 
for timing in motion. Even with 3, your fix and time performance is degraded. 
Chugging 
in and out of holdover has it’s impact. 

Do you want to use multiple systems? If you are running a mixed mode system, 
you can go 
from 100% GPS to 100% GLONASS to 100% BEID0U due to viewing angle.  That tosses
a whole *bunch* of issues into the mix. 

How fast are you going? Moving around can involve move 100’, stop and wait for 
a day or
it can involve something moving at mach 3. By far the most common for a GPSDO 
is some 
sort of car, truck, or military vehicle on the highway. There are many other 
possibilities.  

Lots of variables. Lots of things to get into the mix in addition to the basic 
nav math.

Bob


> On Oct 17, 2016, at 12:19 AM, Joseph Gray  wrote:
> 
> I'm curious to know how accurately a GPSDO will keep its 10 MHz output
> while moving. No initial survey to set a position would be done. I
> don't care about the UTC time.
> 
> Joe Gray
> W5JG
> ___
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Re: [time-nuts] Moving GPSDO

[Magnus Danielson]

Joe,

In T-mode, the location in X, Y and Z is assumed known so those values 
is used as constants in producing the T difference between a satellite 
and the GPSDO. As you now move your receiver from the original X, Y and 
Z those location errors will translate into time errors. The worst of 
this will the T-RAIM hopefully clip out, but for the remaining the 
errors might drive the receiver all over the place, and as it shifts 
around so will the frequency. It won't be a pretty picture.


What you should do, if you can, is to go out of T-mode into normal 
tracking. Choosing the speed-grade of your movement can be worth some 
effort. Far from all GPSDOs can do this, since they typically is 
intended for fixed locations.


Potentially can aiding by IMU help some, but very few GPSDOs come close 
to support it. When moving you have to consider other factors of a 
dynamic environment.


I know of only a handful of GPSDOs for dynamic platforms.

Cheers,
Magnus

On 10/17/2016 08:02 AM, Joseph Gray wrote:

Bill,

My question was more generally about any GPSDO, but it's good to know
about the Motorola/Lucent.

What about this scenario - the GPSDO has a fixed position on initial
powerup, but then it is moved periodically or even continuously,
without updating the GPS coordinates. The distance from the original
coordinates could be anywhere from close by, to across the state.
Periodically, a new survey could be run to keep things from getting
too far out in left field.

At some point, I'll have to do some field testing, but I wanted to get
the list wisdom first.

Joe Gray
W5JG


On Sun, Oct 16, 2016 at 11:08 PM, Bill Hawkins  wrote:

The Motorola receivers in Lucent gear won't output a time signal if they
don't have an initial survey.

I make this assertion because the RFTG I had would not lock. The
Motorola bag of bits decodes to say there's no position fix because
enough satellites have not been acquired. Too bad I lived in a valley.

Let us know how this turns out, starting from an initial survey.

Bill Hawkins

-Original Message-
From: Joseph Gray
Sent: Sunday, October 16, 2016 11:20 PM

I'm curious to know how accurately a GPSDO will keep its 10 MHz output
while moving. No initial survey to set a position would be done. I don't
care about the UTC time.

Joe Gray
W5JG

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Re: [time-nuts] Moving GPSDO

[Hal Murray]

jg...@zianet.com said:
> What about this scenario - the GPSDO has a fixed position on initial
> powerup, but then it is moved periodically or even continuously, without
> updating the GPS coordinates. The distance from the original coordinates
> could be anywhere from close by, to across the state. Periodically, a new
> survey could be run to keep things from getting too far out in left field. 

Most commercial GPSDOs assume they are running at a fixed location and won't 
work very well unless they are near their surveyed location.  Near is 
measured in feet, not miles.  That allows them to work with fewer satellites 
which was important with the GPS receivers in old gear like the TBolt and 
Z3801A.

But that's all software/firmware.  If you build your own GPSDO you can use 
whatever GPS receiver you like as long as it puts out a PPS or something that 
you can lock to.

I think Jackson Labs makes some non-survey GPSDOs.
http://www.jackson-labs.com/index.php/products/lte_lite
The FAQ says there is a non-survey mode.

You might find something interesting in time-nuts archives from about 2 years 
ago.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Moving GPSDO

[Joseph Gray]

Bill,

My question was more generally about any GPSDO, but it's good to know
about the Motorola/Lucent.

What about this scenario - the GPSDO has a fixed position on initial
powerup, but then it is moved periodically or even continuously,
without updating the GPS coordinates. The distance from the original
coordinates could be anywhere from close by, to across the state.
Periodically, a new survey could be run to keep things from getting
too far out in left field.

At some point, I'll have to do some field testing, but I wanted to get
the list wisdom first.

Joe Gray
W5JG


On Sun, Oct 16, 2016 at 11:08 PM, Bill Hawkins  wrote:
> The Motorola receivers in Lucent gear won't output a time signal if they
> don't have an initial survey.
>
> I make this assertion because the RFTG I had would not lock. The
> Motorola bag of bits decodes to say there's no position fix because
> enough satellites have not been acquired. Too bad I lived in a valley.
>
> Let us know how this turns out, starting from an initial survey.
>
> Bill Hawkins
>
> -Original Message-
> From: Joseph Gray
> Sent: Sunday, October 16, 2016 11:20 PM
>
> I'm curious to know how accurately a GPSDO will keep its 10 MHz output
> while moving. No initial survey to set a position would be done. I don't
> care about the UTC time.
>
> Joe Gray
> W5JG
>
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Re: [time-nuts] Moving GPSDO

[Bill Hawkins]

The Motorola receivers in Lucent gear won't output a time signal if they
don't have an initial survey.

I make this assertion because the RFTG I had would not lock. The
Motorola bag of bits decodes to say there's no position fix because
enough satellites have not been acquired. Too bad I lived in a valley.

Let us know how this turns out, starting from an initial survey. 

Bill Hawkins 

-Original Message-
From: Joseph Gray
Sent: Sunday, October 16, 2016 11:20 PM

I'm curious to know how accurately a GPSDO will keep its 10 MHz output
while moving. No initial survey to set a position would be done. I don't
care about the UTC time.

Joe Gray
W5JG

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[time-nuts] Moving GPSDO

[Joseph Gray]

I'm curious to know how accurately a GPSDO will keep its 10 MHz output
while moving. No initial survey to set a position would be done. I
don't care about the UTC time.

Joe Gray
W5JG
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