On 10/21/2011 12:05 AM, WarrenS wrote:
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 difference logger).
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.
Results:
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 is use.
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
I like this idea. I would need a couple of thunderbolts to try it.
A side-effect is that the transfer oscillator also provides a UTC source.
Care should be taken such that the same birds is selected. I think a
normal mode T-bolt should be used as normal reference and bird-master,
and the selection be forced onto the slave measurement channels. Would
not require very much of a software.
Only works for 10 MHz clocks I guess.
The software could produce a socket for timelab or it could provide data
on a timelab compatible file, since timelab is able to get data from an
updating file.
The overall processing and parsing should be fairly simple to produce
the raw-data. Sounds like a fun project.
Anyone with a few spare thunderbolts that I could get to try this out?
Bad oscillator isn't a problem.
Cheers,
Magnus
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