[time-nuts] new GPSDO kit
SAIDJACK at aol.com
SAIDJACK at aol.com
Sat Apr 5 14:19:55 EDT 2014
>>Can you say more about what this means?
>>"It generates a low-noise 10MHz signal with typically better than
>>1E-010 precision and accuracy (0.1ppb) on average"
let me explain. I took some measurements over night, see attached files.
This was done with the unit shielded from airflow and sitting on a bench, and
the time constant increased by a bit to account for the benign no-airflow
You can see that the ADEV at any time from 1s to 10,000s averages and
beyond is about 1.3E-010 worst case. So you can assume that the average
accuracy (because of GPS being the absolute reference) and relative precision (the
ADEV around the average value) is about 1.xE-010 on a typical unit.
Also note that the second plot shows a standard deviation of the TI
interval of 13.3ns which is significantly better than the 25ns spec.
Lastly, the performance of 3E-012 at 10,000s is almost 3x better than spec.
This was a random unit I grabbed that had been sitting on a shelf for some
months, and I only let it run for ~15 minutes after power-on before I
started the measurement.
This is one of the beautiful features of the TCXO we use: it does not
require long retrace and warmup periods. It runs pretty much right out of the
box, even after months in storage. An OCXO based unit probably would have
required 8+ hours to stabilize from its retrace after such a long off-period.
In fact this unit ran at only about 1.5ppb error before disciplining
started, meaning the TCXO and our firmware kept that frequency accuracy over
several months on the shelf without power.
So you could go to a work-site, set up the unit and wait about 15 minutes,
then get a really clean, accurate, and stable reference signal.
Hope that makes sense,
In a message dated 4/4/2014 16:40:45 Pacific Daylight Time,
brooke at pacific.net writes:
Can you say more about what this means?
"It generates a low-noise 10MHz signal with typically better than 1E-010
precision and accuracy (0.1ppb) on average"
SAIDJACK at aol.com wrote:
> Hello everyone,
> sorry for the plug, but we just announced a new $568 complete GPSDO
> reference kit.
> This unit is a tiny desktop unit with 10m antenna, power supply, cables,
> CD, and other accessories. It is a low cost addition to our Fury GPSDO
> and contains a really good TCXO, a uBlox GPS receiver, and various power
> options. I believe this is the lowest-cost real GPSDO in mass production
> available on the market right now, and being a true GPSDO it has some
> good phase noise and stability specs.
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