[time-nuts] Frequency Stability of Trimble Mini-T
SAIDJACK at aol.com
SAIDJACK at aol.com
Thu Oct 16 20:23:31 UTC 2008
let me take the commercial discussion offline with you, and let me try to
answer the time-nuts questions for you:
> When you say the EFC voltage changes by several millivolts, how much
> does that change the crystal frequency?
Actually, the average frequency doesn't change at all, it is being held at
10.0MHz by the GPS reference. What does change is the control voltage that the
crystal wants to see to generate exactly 10.0MHz.
But let's say you kept the EFC voltage constant, say by disconnecting the
GPS antenna, then it is simple to calculate the frequency change the OCXO
experienced due to the jump:
Say there was a 500 Microvolts jump. A typical OCXO has +/-20Hz control
range 0V to 5V. So it's sensitivity is 8Hz/V. Now simply multiply this by
8Hz/V * 0.5mV = 0.004Hz change of frequency
Or in other words, 0.004Hz/10MHz = 4E-010 change in frequency.
That doesn't sound significant, but would show up as a significant jump on
GPSCon for example.
> if it is not confidential, can you say what kind of phase detection
> you use in your GPSDO?
That's a little bit confidential unfortunately :)
> On your page at http://www.jackson-labs.com/products_fury.html
> it states:
> "Allan Deviations of less than 1E-011 are possible for measurement
> intervalls greater than 0.1 seconds."
> What kind of counter do you use to measure that data point?
You can find several review papers of Jackson Labs' products written by Tom
Van Baak on his website. He was kind enough to supply ADEV plots for our Fury
units, and our double oven units achieve this level of performance. I think
he used 53132A's for some of these plots, and TSC5120A units for the ADEV
See for example his review of an early version of the Fury:
Please note that Tom tested an early version of the Fury firmware, and we
have since very significantly improved the performance of the unit.
> Further down on the same page, it states:
> "A high-end Motorola GPS receiver"
> Can you tell what kind of Motorola GPS you use?
Fury uses the M12+ and/or M12M GPS. They are now made by iLotus since
Motorola sold their GPS operations. We also use modern 3D-capable 50-channel GPS's
on our newer products such as the FireFly series GPSDO.
>Finally, do you have a price list for the OEM and commercial
I will have our VP of sales discuss this with you, and send you a price list
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