On 11/04/14 21:38, Chris Albertson wrote:
Look at what NTP does to select "good" clocks when it has many to choose
from. It does not simply average them.
It looks at the noise in each one and then sees which clocks have
overlapping error bars. It assumes that all good clocks have the same tim
On 11/04/14 15:33, Tom Van Baak wrote:
Brooke, Ulrich,
Keep in mind the hp SmartClock product line dated from the early-90's and it was one of
the first GPSDO on the market. So even simple things like using timing receivers, partial
ionospheric correction, sawtooth correction, sub-ns TIC, 1PPS
Look at what NTP does to select "good" clocks when it has many to choose
from. It does not simply average them.
It looks at the noise in each one and then sees which clocks have
overlapping error bars. It assumes that all good clocks have the same time
within limits of their precision. Then f
Ulrich
Thanks for posting the reference.
Very interesting and useful. The clues they give sounds like enough
information to do the Smartclock loop control things that they talk about.
ws
***
Hi Brooke,
HP had some way around SA that improved the timekeeping.
HP cal
Interesting idea. It might be an interesting experiment to couple a large
number of inexpensive xtals to see how it impacts effects such as sudden
changes in a single xtal.
With sufficient monitoring of each one, you could even tune the coupling to
amplify/attenuate the results of the 'good' a
On 4/11/2014 11:04 AM, Hal Murray wrote:
How many would you need? Is 3 enough?
How well could you do with several low(er) cost oscillators relative to one
good but expensive one? It might be an interesting experiment in a nutty
sort of way.
My guess would be 3 would be a minimum, so you
co
rich...@karlquist.com said:
> Still, there was no way to guarantee that a crystal in the future would
> never have a jump or sudden change in aging.
> What was really needed was an ensemble of oscillators, but that was not
> economically competitive with rubidium.
How many would you need? Is 3
6
An: Tom Van Baak; Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] GPSDO & Crystal Aging
Hi Tom:
That makes sense because the GPS was just coming on line and
not anywhere near a full compliment of satellites and SA
was on.
HP had some way around SA that improved t
ent
time on firmware disassembly.
/tvb
- Original Message -
From: "Ulrich Bangert"
To: "'Discussion of precise time and frequency measurement'"
Sent: Friday, April 11, 2014 3:06 AM
Subject: Re: [time-nuts] GPSDO & Crystal Aging
> Hi Brooke,
>
&
Tom Van Baak; Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] GPSDO & Crystal Aging
>
>
> Hi Tom:
>
> That makes sense because the GPS was just coming on line and
> not anywhere near a full compliment of satellites and SA
> was on.
&
Hi Tom:
That makes sense because the GPS was just coming on line and not anywhere near a full compliment of satellites and SA
was on.
HP had some way around SA that improved the timekeeping.
Has that ever been disclosed?
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernm
In message , "Tom Van Baak" writes:
>True, except that in most cases the long-term frequency drift rate
>is so tiny compared to all the short- and mid-term instability that
>it is not worth worrying about.
... unless you care about holdovers of multiple days or weeks.
Otherwise: I fully agree.
Hi Brooke,
True, except that in most cases the long-term frequency drift rate is so tiny
compared to all the short- and mid-term instability that it is not worth
worrying about. In other words, I agree it is modeled as a "linear ramp", but
the ramp, even at huge timescales, is so close to flat,
Hi:
AFAICR the HP GPSDOs included the idea of measuring the aging rate of the crystal and applying that correction during
holdover.
This was also mentioned by Brooks Shera in relation to his GSPDO (there was a plot), but I don't think it was part of
the firmware?
So rather than just locking t
14 matches
Mail list logo
