On Sat, 22 Mar 2014 07:40:27 -
David J Taylor david-tay...@blueyonder.co.uk wrote:
From: Hal Murray
There is a newer system getting phased in: ADS-B
http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast
The plane broadcasts it's position and velocity every second.
On Sat, 22 Mar 2014 06:58:22 -0700 (PDT)
J. Forster j...@quikus.com wrote:
I'm not so sure it is worth much as parts, except possibly on the
black market. I believe the aircraft industry is big on tracking
every part, cradle to grave. After all an under spec bolt can cause a
very expensive
In message 20140323014515.0fffd232@linux-wh01, nuts writes:
These salvage yards
knew the content of each bird down to a science, and thus know when to
start the process.
We had an interesting event in Denmark related to that: Somebody hadn't
heard about Mag-Thor, and tried to drive a truckload
An idea is struggling to take shape in my fevered brain. I'd like to
check some foundation assumptions.
1. The difficulty with disciplining a local oscillator to a GPS signal
is due to variations in the received GPS signal and the LO.
2. The variations occur slowly, as crystal aging, and
From: nuts
Note that the ADS-B mentioned is just a fancy version of the
transponder that was turned off.
I ran into your R Pi page about halfway in the process of doing my
Beaglebone Black RTLSDR page. I have RTLSDR and dump1090 running on
Angstrom Linux. I bought the GPS you suggested and will
There is a newer system getting phased in: ADS-B
For info MH370 did transmit ADS-B signals up to 17:21 UTC on 7 March when it
seems it was either switched off or disabled. You can still see the track
it took up to this time using the playback facility on Flight Radar 24 by
say starting
Bill wrote:
1. The difficulty with disciplining a local oscillator to a GPS signal
is due to variations in the received GPS signal and the LO.
I'm not sure I'd call that the difficulty -- it is the task of a
GPSDO to discipline the local oscillator *at time scales where the
GPS is better
Hi
The real answer is always “that depends”.
1) How much does the sensitivity of your OCXO change with a change in EFC?
1.4:1, 2:1, 4:1 …. (slope sensitivity not % linearity)
2) How quiet is your DAC compared to your OCXO?
3) How quiet is your reference compared to your OCXO?
4) How much
Da: rmon...@bigpond.net.au
Data: 23/03/2014 10.58
For info MH370 did transmit ADS-B signals up to 17:21 UTC on 7 March when it
seems it was either switched off or disabled. You can still see the track
it took up to this time using the playback facility on Flight Radar 24 by
say starting at
On 23/03/14 06:56, Said Jackson wrote:
Tom,
In my experience one of the biggest GPSDO error sources in low-cost and even
some higher end OCXOs is oscillator hysteresis. Which can change with operating
temperature, operating time (crystal age) and even over crystal tilt.
Does your OCXO model
On 23/03/14 14:02, Bob Camp wrote:
Hi
The real answer is always “that depends”.
1) How much does the sensitivity of your OCXO change with a change in EFC?
1.4:1, 2:1, 4:1 …. (slope sensitivity not % linearity)
2) How quiet is your DAC compared to your OCXO?
3) How quiet is your reference
Hi
One thing that should be noted. Some of this stuff has zero impact at long tau.
Some of it only has an impact at long tau. It might be easier to split a model
into long and short versions to deal with this stuff.
Getting the data is the next step. You can find app notes on some voltage
On Sun, Mar 23, 2014 at 3:37 AM, nuts n...@lazygranch.com wrote:
Note that the ADS-B mentioned is just a fancy version of the
transponder that was turned off.
I guess it depends on your concept of what a transponder does. Yes, ADS-B
does transmit in the same band as the standard transponder
To handle higher tau performance I think we want a higher degree loop.
Cheers,
Magnus
Is a higher degree loop possible while maintaining stability? Commanding
frequency while measuring phase is one pole, integrating the result of the
phase comparison is a second pole and closing the loop will
I agree.. Had a maybe weird thought. Computing power is now a trivial part
of the problem, in that a Ras.Pi can be put to the task for $35 or so. In
that case, PIDdling with time constants and such in a feedback loop with phase
difference as the error signal is easily done, either in
I agree.. Had a maybe weird thought. Computing power is now a trivial part
of the problem, in that a Ras.Pi can be put to the task for $35 or so. In
that case, PIDdling with time constants and such in a feedback loop with phase
difference as the error signal is easily done, either in
I agree.. Had a maybe weird thought. Computing power is now a trivial part
of the problem, in that a Ras.Pi can be put to the task for $35 or so. In
that case, PIDdling with time constants and such in a feedback loop with phase
difference as the error signal is easily done, either in
I agree.. Had a maybe weird thought. Computing power is now a trivial part
of the problem, in that a Ras.Pi can be put to the task for $35 or so. In
that case, PIDdling with time constants and such in a feedback loop with phase
difference as the error signal is easily done, either in
sorry! had a glitch and hit send too many times :-)
--
The power of accurate observation is commonly called cynicism by those who
have not got it.
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
Skype: buffler2
Hi
Unless you can include all the second and third order effects in your model,
there will still be a lot to “learn” as you build your gizmo. Computing power
is still impacted by garbage in / garbage out.
Bob
On Mar 23, 2014, at 12:07 PM, Don Latham d...@montana.com wrote:
I agree.. Had a
NTP is best used over the Internet. It was designed for unreliable data links.
In the quest for expansion of NTP over the internet, one thing has always
nagged me.
You can find lists of servers and they will give a physical location along with
other info about them...
Big whoop... Often
Hi
You can (and many do) run through a list of servers with an NTP client and see
what you get. It’s a bit of work, but you only do it once.
———
I suspect that what NIST is looking for is somebody in the cloud business
(Amazon, Google, Microsoft, IBM) to step up and mention that they have
On Sun, Mar 23, 2014 at 9:26 AM, Jason Rabel
ja...@extremeoverclocking.com wrote:
If there was some sort of feature in NTP (maybe there already is???), or even
a separate program that could test a list of NTP
servers to try and pick the lowest latency, I think that could have a
positive
On Sat, Mar 22, 2014 at 6:34 PM, Paul tic-...@bodosom.net wrote:
E.g. FSM says their NTP+PTP servers perform equally well using either
protocol. The trick is to use optimized NTP software and timestamping
hardware.
Yes. If you modify NTP so that is does the same thing as PTP then it
will as
On Sat, Mar 22, 2014 at 8:18 PM, Don Latham d...@montana.com wrote:
Hi Tom et.al. Isn't the simulator easily convertible to the real thing?
That is, data inputs should be convertible somehow to data streams from
physical devices?
Don
This is a very common development method, not just with
On Sun, Mar 23, 2014 at 1:08 PM, Bob Camp li...@rtty.us wrote:
I suspect that what NIST is looking for is somebody in the cloud business
(Amazon, Google, Microsoft, IBM) to step up and mention that they have
2,989,875 server racks scattered about the world and they would be happy to
run NTP
4) How much do the DAC, reference, op-amps, resistors, capacitors, drift with
time?
Assuming constant temperature and supply voltage...
What is the time scale for parts drifting? Is it very low frequency so well
within the loop bandwidth or is it jumps that will be hard to filter out?
Hi
There are many issues when it comes to a GPSO. But what has to be first
discussed what is it one wants to accomplish. Last year when we worked on the
latest Shera GPSDO we always got better than 1E-11 with a unit lying on
the bench with no enclosure or thermal management.
Chasing
Hi
If you have a source of “noise” that is not in your model *and* it’s
significant, then your model will not predict the outcome. That’s true if it’s
in or if it’s outside the loop bandwidth.
Bob
On Mar 23, 2014, at 2:27 PM, Hal Murray hmur...@megapathdsl.net wrote:
4) How much do the DAC,
On Sun, Mar 23, 2014 at 1:37 PM, Chris Albertson
albertson.ch...@gmail.comwrote:
Yes. If you modify NTP so that is does the same thing as PTP then it
will as good as PTP. That should be obvious.
I believe you misunderstand my point.
___
time-nuts
Jim wrote:
Is a higher degree loop possible while maintaining stability?
Sure. PLL control loops (and other feedback loops) are often
designed out to fourth and fifth order. Very simply put, the
requirement is that the loop must have a reasonable phase margin at
the frequency where the
I'm working on a GPSDO but with different goals. I want mine to be
1) very low cost, under $50 for everything if I can
2) No PCB required.
3) very easy to replicate by a first time builder
4) Easy to understand. The parts count is very low, no exotic parts
and the software written very clearly
I will be eager to see responses to this. It is similar to the behavior
I was seeing on my tested nortel unit that I purchased from the
e-place. Tried a bunch of things, new antenna, higher antenna (even
though my Z3801 worked fine on the old, before the Z3801 died) and
different power
You are nine days too early.
:)
Tom
- Original Message -
From: Chris Albertson albertson.ch...@gmail.com
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Sunday, March 23, 2014 5:26 PM
Subject: Re: [time-nuts] GPSDO control system
I'm working on a
FR24 got a bit picky with their latest generation receiver since so
many of the first generation units walked. What they have been doing
lately is giving them to flight schools, which are a bit more
responsible than your average schmuck.
You can monitor any of these decoders with
Hi
While you would *think* that LTE and PCS signals would be locked to “something
good”, that’s not always the case. If you decide to use something like this for
timing, it’s best to check things out carefully. Symmetricom learned this the
hard way on one of their boxes ….
Bob
On Mar 23,
Chris wrote:
4) why use a PPS as the communications link from GPS to GPSDO?
Generally, because that is the only precision timing output you get
from a GPS unit. The models with a 10kHz output were prized by the
simple GPSDO crowd precisely for the fact that the phase-locked
10kHz signal
Hi,
can anyone out there point me to a source
for the exact time of the equinoxes and solstices
so that I can synchronise a sidereal clock?
I assume that at some time the Universal Time we use
is exactly the same as Sidereal time, and so a Sidereal clock
could be set.
I have a Tbolt producing
li...@rtty.us said:
If you have a source of noise that is not in your model *and* its
significant, then your model will not predict the outcome. Thats true if
its in or if its outside the loop bandwidth.
Does anybody have data on the drift of Rs or Cs? In this context, is it
On Sunday, March 23, 2014, Neville Michie namic...@gmail.com wrote:
Hi,
can anyone out there point me to a source
for the exact time of the equinoxes and solstices
so that I can synchronise a sidereal clock?
Check the USNO's website.
--
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Hal wrote:
Does anybody have data on the drift of Rs or Cs?
Tom has some data posted at leapsecond.com (for H-masers, too).
John Miles has some at ke5fx.com.
John Ackermann has some at febo.com.
I encourage you to roam widely over all three sites -- you will be
well rewarded.
Best
csteinm...@yandex.com said:
Can I find a way to move the OXCO into the guts of a GPS receiver.
I don't know. Can you? That is essentially what the Thunderbolt does, and
it brings with it the tremendous advantage that it removes the sawtooth
error -- which is why some of us think so
On 24/03/14 00:08, Charles Steinmetz wrote:
Chris wrote:
4) why use a PPS as the communications link from GPS to GPSDO?
Generally, because that is the only precision timing output you get from
a GPS unit. The models with a 10kHz output were prized by the simple
GPSDO crowd precisely for the
Go to The Astronomical Almanac:
asa.usno.navy.mil
---
Antonio A.S. Magalhaes.
Em 2014-03-23 23:02, Neville Michie escreveu:
Hi,
can anyone out there point me to a source
for the exact time of the equinoxes and solstices
so that I can synchronise a sidereal clock?
I assume that at some time
Jim,
On 23/03/14 16:00, Jim Miller wrote:
To handle higher tau performance I think we want a higher degree loop.
Cheers,
Magnus
Is a higher degree loop possible while maintaining stability? Commanding
frequency while measuring phase is one pole, integrating the result of the
phase
Jason,
On 23/03/14 17:26, Jason Rabel wrote:
NTP is best used over the Internet. It was designed for unreliable data links.
In the quest for expansion of NTP over the internet, one thing has always
nagged me.
You can find lists of servers and they will give a physical location along with
On Sun, Mar 23, 2014 at 7:02 PM, Neville Michie namic...@gmail.com wrote:
can anyone out there point me to a source
for the exact time of the equinoxes and solstices
I think you want this: http://aa.usno.navy.mil/data/docs/geocentric.php
e.g. RA 0 is 2014 Mar 20 16:57:07.5 or RA 12 is 2014
I've lost track now of who it was, but someone asked if there was a
better strategy than a GPS disciplined quartz oscillator or a GPS
disciplined rubidium. My best standard uses an SRS PRS10 rubidium
disciplined by GPS PPS at tau = VERY long ( ~12 hours), using the
PRS10's internal PPS
Bob,
The sawtooth is generated by the granularity of the GPS receiver clock
not being synchronous with the recovered PPS. The receiver program can
calculate the correction to be applied to the next PPS and outputs it in
a message, bu only in timing receivers, this is not a useful thing in
Rule of thumb:
- really good OCXO have frequency drift rates of 1e-10 to 1e-11/day
- common Rb have frequency drift rates on the order of 1e-11/month
- Cs do not have frequency drift
- H-maser drift rates are 1e-15 to 1e-16/day
/tvb (i5s)
On Mar 23, 2014, at 4:32 PM, Charles Steinmetz
Hi
…. and GPS has cyclic issues on a 24 / 48 hour basis ….
Bob
On Mar 23, 2014, at 8:58 PM, Tom Van Baak (lab) t...@leapsecond.com wrote:
Rule of thumb:
- really good OCXO have frequency drift rates of 1e-10 to 1e-11/day
- common Rb have frequency drift rates on the order of 1e-11/month
-
Hi Ignacio,
Thanks for the response. I've got a UT+ in the parts box. But that's not the
problem I'm trying to solve. I'm trying to make the best GPSDO that I can make
using a nav receiver at the moment. Call it an obsession if you like. It's OK
if I don't have corrections to the
What you are seeing in position error is a random noise. There is no
pattern to it and it is not predictable. A sawtooth error is very
nice and regular looking. It's not noisy and can be predicted in
advance.Possition error is not at all like sawtooth.
I think what you CAN do is look at
Random noise or not, wouldn't a position error in a nav receiver cause a
corresponding displacement of the 1PPS pulse?
Also there's a bit more to it than just minor noise. It's probably multipath,
or perhaps even jammers passing on the freeway about a mile away. Whatever the
cause, take a
Hi Charles,
How do you lock your OCXO to the PRS10?
Thanks,
david
I've lost track now of who it was, but someone asked if there was a
better strategy than a GPS disciplined quartz oscillator or a GPS
disciplined rubidium. My best standard uses an SRS PRS10 rubidium
disciplined by GPS PPS
It's not really stratum based. The clock selection algorithm is described
here
http://www.eecis.udel.edu/~mills/ntp/html/select.html
Basically it allows every clock that can logically contribute That means
with estimated error bounds that over lap.
That with those not eliminated nTP applies a
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