[time-nuts] DMTD using TBolts
warrensjmail-one at yahoo.com
Thu Oct 20 22:05:00 UTC 2011
Tbolt-Tic is what I call a Tbolt when it is NOT used as a GPSDO controller
but instead used as a high resolution time interval counter. (really a time
How do you make a single TBolt-Tic much better?
Simple, By making a dual TBolt-Tic.
>From an offshoot of my Common view TBolt experiments,
I connected a common GPS antenna to two Tbolts that both have been modified
to use an external osc.
This makes a simple, high performance, DMTD tester with low ps resolution
using the 'noisy' GPS signal as the common "offset" Osc.
DMTD and common view both work on the same basic principle.
The end results is that the noise of the common signal source (GPS in this
case) tends to cancel when the difference between the two Tbolt data streams
The data difference then gives the freq and the phase difference between the
two 10 MHz Oscillators that are being compared. (neither of which needs to
be disciplined or have an EFC input).
>From the phase difference and the PPT Freq difference data, standard low
noise floor ADEV plots can be made with tau zero = 1 sec.
No software yet to make it all easy and automatic, but hopefully that will
happen in a future version of LadyHeather and/or TimeLab.
Maybe, the existing Plotter S/W can already take the raw data from two
Tbolts, find the differences by subtracting both the Phase and PPT columns
and plot the results.
If not, any volunteer to come up with a SIMPLE routine to do the above
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