He should be looking at Wenzel Associates and NEL.
Wenzel specs -170 dBc at 100 Hz offset. Hope he has lots of money for
this one. Some of the NEL OCXO's are $5,000 and 6 months to 1 year
delivery. Both vendors also sell noisier cheaper versions.
He needs to trade off noise vs offset vs cost
Hi
Rb and low phase noise ( at least far removed ) are sort of mutually
exclusive specs. You need to pick one …
Assuming the decision is to go for the -170 dbc/Hz spec, Congratulations
you are buying on OCXO. Not quite clear which OCXO, but it’s pretty likely
to be an OCXO. (Yes, there are exc
I'm looking for suggestions for AC-powered 10 MHz sinewave laboratory
signal sources with very low phase noise, having a noise floor below
-170 dBc/Hz. Rubidium is desired, but not essential. Reliability
and durability in lab use is essential.
Which makes and models should I consider purchasi
All,
Ahhh, Yes. Checking notes, during the initial build I slapped a pair of
10pF caps down (all I had on hand) just to get the RTCC oscillators
somewhat working. I can see now that is WAY under needed capacitance.
Measurements are taken right in the micro, so no external leads to
influence
A Search at eBay or a general Google search on the Internet
will reveal a number of older GPS modules used for timing (used & new)
A recent eBay search revealed a group of five (5) uBlox-4T modules for $24
(free ship).
eBay Auction number: 203426846312
uBlox LEA-4x series GPS receiver Data Sheet
Hi
The typical 32 KHz crystal has a parabolic tempco. It peaks at kinda
sorta room temperature. This makes it work pretty well on a normal
wrist.
As you get away from ~ 25C, the frequency drops. Since it’s a
parabola, the further away from room you get the faster it drops.
Something in the 1
Hi
GPS modules tend to be “accuracy rated” in terms of what they
do when fed with a signal generator. The “accuracy” is the departure
from the reference pulse out of the generator. Oddly enough it does
not include all of the delays involved ( yes that’s a bit weird).
When you feed them with rea
No one mentioned tempco, so I will. Ideally you should do your
calibration at a temperature corresponding to the long term
average in your workshop. If the crystal is in a piece of
equipment with a temperate rise, it should be accounted for,
and then going forward you have to leave the equipment
Lux, Jim writes:
> Can one discipline a geyser to an external source?
>
>a) I assume there's some data somewhere on eruption timing - sure, Old
>Faithful is quite regular, sufficiently that they can say "the next
>eruption will occur at" and people will gather and watch it.
Last I hear
Hi
Well, specific to Old Faithful ….
They look at the current eruption and rate it for height and duration.
Based on that rating, they make a guess about the wait for the next
one. Their guess is typically a +/- 10 minute sort of thing. Very much
like predicting the weather.
https://www.nps.
Am 2022-04-01 15:09, schrieb Lux, Jim:
As I re-read Fleming's "You Only Live Twice" last night, which
features a geyser that is "regulated" by a valve of some sort I was
intrigued by this idea:
Can one discipline a geyser to an external source?
The original Geysir in Island has become lazy. It
I've attached the ADEV plot from 11 years of Old Faithful data (2001 to
2011).
For the data and also a deep dive into geyser statistics see this
wonderful article:
http://www.stat.yale.edu/~jah49/Pictures_in_R/Fickle_Old_Faithful/OldFaithful.pdf
These papers might also be interesting to you:
Nice, I'm trying to do something similar. But without the PICdiv or the
TIC measurement. Only the GPS PPS into the STM32 and the stabilized PPS
is generated by a timer in the STM32
First step was to measure against the running average of the GPS PPS.
As can be seen in attached Timeplot measureme
So reading a little bit about the "three cornered hat method", it assumes
the errors in the three datasets are not correlated, which in the case of
testing three different GPSDOs is obviously not the case. However we
already have estimates of the magnitude of the error introduced by the GPS
PPS: I
In summary, to measure the accuracy or stability of any clock, you always
need... a better clock. Or you can use the "three cornered hat" method, but
it requires that the accuracy or stability of the three devices under test
**should not be correlated**.
On Fri, Apr 1, 2022 at 1:58 AM Bob kb8tq w
As I re-read Fleming's "You Only Live Twice" last night, which features
a geyser that is "regulated" by a valve of some sort I was intrigued by
this idea:
Can one discipline a geyser to an external source?
a) I assume there's some data somewhere on eruption timing - sure, Old
Faithful is quit
Hi,
If you do not want to make it a time-nuts style research project, but just
look for a quick fix - here is a rule of thumb:
This kind of crystal usually has a trimming sensitivity of around -10
ppm/pF. This means, if you increase the value of both capacitors on either
side by 2 pF will increase
Remember that the load cap value in the data sheet isn't what you fit in
the circuit.
First deduct the total stray capacitance on the pcb and the IC
connections, then double the remainder... that's the value you place
either side of the crystal.
E.g. if the data sheet says 12.5pF and you estim
Hi All,
Bob is right. This is very much a cut-and-try thing for a couple of reasons.
1. Crystals with the same printed specs from different manufacturers respond
differently.
2. Stray capacitance in the specific installation is part of the total load
capacitance. Every installation is differen
Hi
Given the (very normal) lack of information on the crystal,
it becomes a “try it and see” sort of thing. They seem to
want 12.5 pf as the load cap for the first one listed on the
data sheet. How far off of that is your circuit as it sits?
First step would be to take the “output” cap up one v
Hi,
I've got a 32.768Khz (USA number format) crystal on a RTCC oscillator of
a small micro, and it's running fast. Around 10 seconds per day or so.
This is a bit more than an order of magnitude more than the datasheet
states.
The 9 seconds per day error should be a good measurement. The RTCC
Hi
The drift used in the original example is just one of many many things
that can come up. There are a lot of “corner cases” in GPSDO design.
The constellation does “this” and they all react. Ideally they would react
to suppress whatever the issue is. It does not always work out that way.
This
nea...@gmail.com said:
> And, I assume that since we have no idea if the used rubidium oscillator from
> ebay is working properly anymore (aside from output seen on a counter), then
> we should take that rubidium oscillator to a calibration vendor and pay them
> to test it, correct?
I think an
Hi
The simple answer is to use your three corner hat approach and
use a different source for each of the corners. Possibly a cheap
Rb for one and a fairly good OCXO for another. Then make your
GPSDO the third corner.
No, you don’t eliminate all questions this way, but you do address
the common
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