Howdy Charles,
Could you tell us more about the PLL, what sort of phase comparator,
filters and so forth. I'd be keen to duplicate and test your configuration.
Thanks,
david
David wrote:
How do you lock your OCXO to the PRS10?
I just use a 1:1 PLL. Some will argue that phase
Does anybody have data on the drift of Rs or Cs?
Rule of thumb:
...
Ah, thanks. But by Rs and Cs I meant plural or R/resistor and C/capacitor.
I know they change a lot with temperature, but how much do they drift if the
temperature is constant?
--
These are my opinions. I hate spam.
David wrote:
How do you lock your OCXO to the PRS10?
I just use a 1:1 PLL. Some will argue that phase locking two
oscillators running at the same frequency is not optimal, but I have
found that it can work very well. YMMV. Perhaps locking a 100 MHz
OCXO to the PRS10 and dividing its
Hi
Which R’s and C’s did you buy? There are a *lot* of different types and they
each have their issues. A very common issue is - “they came from the store”.
Any ability to trace them back to a manufacturer and a process has been lost.
Bob
On Mar 24, 2014, at 2:29 AM, Hal Murray
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
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
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,
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
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
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
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
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
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
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 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
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