JR
Jason Rabel
Thu, Sep 9, 2010 6:01 PM
What about Symmetricom XPRO Rubidium? It says on the data sheet they have a low aging rate option (1e-11 / month).
What about Symmetricom XPRO Rubidium? It says on the data sheet they have a low aging rate option (1e-11 / month).
RS
Ralph Smith
Thu, Sep 9, 2010 7:03 PM
1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
Without going to cesium we will most likely need some form of mutually
visible synchronization.
Ralph
On Thu, September 9, 2010 2:01 pm, Jason Rabel wrote:
What about Symmetricom XPRO Rubidium? It says on the data sheet they have
a low aging rate option (1e-11 / month).
1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
Without going to cesium we will most likely need some form of mutually
visible synchronization.
Ralph
On Thu, September 9, 2010 2:01 pm, Jason Rabel wrote:
> What about Symmetricom XPRO Rubidium? It says on the data sheet they have
> a low aging rate option (1e-11 / month).
MJ
Mark J. Blair
Thu, Sep 9, 2010 10:17 PM
On Sep 9, 2010, at 12:03 PM, Ralph Smith wrote:
1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
Without going to cesium we will most likely need some form of mutually
visible synchronization.
How about a rubidium or cesium standard at each site for holdover, with an extra cesium standard that is physically carried from site to site (say, by helicopter) during an extended holdover period to distribute a common time reference around?
Or, a specially-equipped aircraft which is periodically flown along paths visible to multiple antenna sites during an extended holdover in order to adjust out drift based on measured round-trip times between the sites and aircraft? In effect, flying your own low-altitude satellite over the sites when the GPS system is down.
These may be silly ideas, but brainstorming is fun.
--
Mark J. Blair, NF6X nf6x@nf6x.net
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.
On Sep 9, 2010, at 12:03 PM, Ralph Smith wrote:
> 1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
> Without going to cesium we will most likely need some form of mutually
> visible synchronization.
How about a rubidium or cesium standard at each site for holdover, with an extra cesium standard that is physically carried from site to site (say, by helicopter) during an extended holdover period to distribute a common time reference around?
Or, a specially-equipped aircraft which is periodically flown along paths visible to multiple antenna sites during an extended holdover in order to adjust out drift based on measured round-trip times between the sites and aircraft? In effect, flying your own low-altitude satellite over the sites when the GPS system is down.
These may be silly ideas, but brainstorming is fun.
--
Mark J. Blair, NF6X <nf6x@nf6x.net>
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.
SG
Sanjeev Gupta
Fri, Sep 10, 2010 4:23 AM
On Fri, Sep 10, 2010 at 06:17, Mark J. Blair nf6x@nf6x.net wrote:
Or, a specially-equipped aircraft which is periodically flown along paths
visible to multiple antenna sites during an extended holdover in order to
adjust out drift based on measured round-trip times between the sites and
aircraft? In effect, flying your own low-altitude satellite over the sites
when the GPS system is down.
Assuming there are multiple overflights per hour, which are visible at more
than 4(?) sites at the same time, would there be enough information to steer
the clocks?
The correction would not need to be in real time, either.
--
Sanjeev Gupta
+65 98551208 http://www.linkedin.com/in/ghane
On Fri, Sep 10, 2010 at 06:17, Mark J. Blair <nf6x@nf6x.net> wrote:
> Or, a specially-equipped aircraft which is periodically flown along paths
> visible to multiple antenna sites during an extended holdover in order to
> adjust out drift based on measured round-trip times between the sites and
> aircraft? In effect, flying your own low-altitude satellite over the sites
> when the GPS system is down.
>
Assuming there are multiple overflights per hour, which are visible at more
than 4(?) sites at the same time, would there be enough information to steer
the clocks?
The correction would not need to be in real time, either.
--
Sanjeev Gupta
+65 98551208 http://www.linkedin.com/in/ghane
O
Oz-in-DFW
Fri, Sep 10, 2010 5:07 PM
On 9/9/2010 2:03 PM, Ralph Smith wrote:
1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
Without going to cesium we will most likely need some form of mutually
visible synchronization.
Is Cesium even enough? The requirement looks like about 6 parts in
10e-14. That's hydrogen maser territory isn't it?
Given the application you could probably achieve this with fiber
back-haul that you continually range and jitter filter to achieve that
resolution. Not gonna be off the shelf, though. Your could probably
layer data transmission on top of this.
Why not just periodically release a metalized weather balloon as a
calibration target, or use one to lift a calibrated reflector in the
event of an outage? Or pick a conventionally tracked target as a
calibration source?
--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)
On 9/9/2010 2:03 PM, Ralph Smith wrote:
> 1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
> Without going to cesium we will most likely need some form of mutually
> visible synchronization.
Is Cesium even enough? The requirement looks like about 6 parts in
10e-14. That's hydrogen maser territory isn't it?
Given the application you could probably achieve this with fiber
back-haul that you continually range and jitter filter to achieve that
resolution. Not gonna be off the shelf, though. Your could probably
layer data transmission on top of this.
Why not just periodically release a metalized weather balloon as a
calibration target, or use one to lift a calibrated reflector in the
event of an outage? Or pick a conventionally tracked target as a
calibration source?
--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)
PR
Pete Rawson
Fri, Sep 10, 2010 5:47 PM
Can you use tethered balloons at each site to obtain adequate S/N
in their position to permit time calculations to 30ns uncertainty?
Pete Rawson
On Sep 10, 2010, at 11:07 AM, Oz-in-DFW wrote:
On 9/9/2010 2:03 PM, Ralph Smith wrote:
1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
Without going to cesium we will most likely need some form of mutually
visible synchronization.
Is Cesium even enough? The requirement looks like about 6 parts in
10e-14. That's hydrogen maser territory isn't it?
Given the application you could probably achieve this with fiber
back-haul that you continually range and jitter filter to achieve that
resolution. Not gonna be off the shelf, though. Your could probably
layer data transmission on top of this.
Why not just periodically release a metalized weather balloon as a
calibration target, or use one to lift a calibrated reflector in the
event of an outage? Or pick a conventionally tracked target as a
calibration source?
--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)
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.
Can you use tethered balloons at each site to obtain adequate S/N
in their position to permit time calculations to 30ns uncertainty?
Pete Rawson
On Sep 10, 2010, at 11:07 AM, Oz-in-DFW wrote:
>
>
> On 9/9/2010 2:03 PM, Ralph Smith wrote:
>> 1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget.
>> Without going to cesium we will most likely need some form of mutually
>> visible synchronization.
> Is Cesium even enough? The requirement looks like about 6 parts in
> 10e-14. That's hydrogen maser territory isn't it?
>
> Given the application you could probably achieve this with fiber
> back-haul that you continually range and jitter filter to achieve that
> resolution. Not gonna be off the shelf, though. Your could probably
> layer data transmission on top of this.
>
> Why not just periodically release a metalized weather balloon as a
> calibration target, or use one to lift a calibrated reflector in the
> event of an outage? Or pick a conventionally tracked target as a
> calibration source?
>
> --
> mailto:oz@ozindfw.net
> Oz
> POB 93167
> Southlake, TX 76092 (Near DFW Airport)
>
>
>
>
>
> _______________________________________________
> 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.
MJ
Mark J. Blair
Fri, Sep 10, 2010 6:14 PM
On Sep 10, 2010, at 10:47 AM, Pete Rawson wrote:
Can you use tethered balloons at each site to obtain adequate S/N
in their position to permit time calculations to 30ns uncertainty?
Tether a single balloon to three sites to reduce the balloon's displacement due to wind, and then measure its position relative to the three sites by laser or radar ranging! :-D
--
Mark J. Blair, NF6X nf6x@nf6x.net
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.
On Sep 10, 2010, at 10:47 AM, Pete Rawson wrote:
> Can you use tethered balloons at each site to obtain adequate S/N
> in their position to permit time calculations to 30ns uncertainty?
Tether a single balloon to three sites to reduce the balloon's displacement due to wind, and then measure its position relative to the three sites by laser or radar ranging! :-D
--
Mark J. Blair, NF6X <nf6x@nf6x.net>
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.
PR
Pete Rawson
Fri, Sep 10, 2010 10:56 PM
Well; maybe more to it. Ballon tether carries a few watts to transmit
from the ballon altitude to all other sites.
At predetermined times the master site balloon transmits to the other
sites. The other sites respond with their estimated time. The master
provides corrected time.
Knowing past history of path properties & precise (ballon) location
at each transmission (data sent with transmission); the rest should
be easy. The master has to precisely locate its own balloon just
prior to transmitting to the other sites. even if it's balloon is wandering,
a short (10ms) delay to transmit will create negligible error.
Ballons might be at each site to create redundant data & suffer a few
lost ballons while waiting for replacements, or to switch time master.
It might be necessary to update path properties just prior to timing.
Pete Rawson
On Sep 10, 2010, at 12:14 PM, Mark J. Blair wrote:
On Sep 10, 2010, at 10:47 AM, Pete Rawson wrote:
Can you use tethered balloons at each site to obtain adequate S/N
in their position to permit time calculations to 30ns uncertainty?
Well; maybe more to it. Ballon tether carries a few watts to transmit
from the ballon altitude to all other sites.
At predetermined times the master site balloon transmits to the other
sites. The other sites respond with their estimated time. The master
provides corrected time.
Knowing past history of path properties & precise (ballon) location
at each transmission (data sent with transmission); the rest should
be easy. The master has to precisely locate its own balloon just
prior to transmitting to the other sites. even if it's balloon is wandering,
a short (10ms) delay to transmit will create negligible error.
Ballons might be at each site to create redundant data & suffer a few
lost ballons while waiting for replacements, or to switch time master.
It might be necessary to update path properties just prior to timing.
Pete Rawson
On Sep 10, 2010, at 12:14 PM, Mark J. Blair wrote:
>
> On Sep 10, 2010, at 10:47 AM, Pete Rawson wrote:
>> Can you use tethered balloons at each site to obtain adequate S/N
>> in their position to permit time calculations to 30ns uncertainty?
>
>
> Tether a single balloon to three sites to reduce the balloon's displacement due to wind, and then measure its position relative to the three sites by laser or radar ranging! :-D
>
>
>
>
> --
> Mark J. Blair, NF6X <nf6x@nf6x.net>
> Web page: http://www.nf6x.net/
> GnuPG public key available from my web page.
>
>
>
>
>
> _______________________________________________
> 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.
