[time-nuts] Common View Tbolt-Tic

Ed Palmer ed_palmer at sasktel.net
Wed Oct 19 03:05:50 EDT 2011


What do you see when you look at the ADEV of a Tbolt in the Disabled 
state?  To me it looks like an ordinary OCXO.  In my case, the aging 
looks like about 5E-10 per day.  The Tbolt book doesn't say much about 
the Disabled state.  Is it possible that the Disabled state means 
'Disable the GPS and pretend that it's just an OCXO'?  If so, this is 
not the mode you want to be in for a Common View test.  By comparison, 
the ADEV of a Tbolt in the TPLL mode looks a lot like a bare GPS 
receiver.  Would that work better for what you want to do?

By the way, regarding Glonass receivers, did you see that there's a 
relatively cheap Glonass/GPS bare receiver board (not a GPSDO) on eBay?  
Item # 300287488541 .  Be warned, a quick Google search suggests that 
the RS-232 output is in an unknown format.

Ed

On 10/18/2011 12:32 PM, WarrenS wrote:
> I'm doing some experiments in hopes of using the TBolt-Tic in a common view configuration to lower the short term noise.
> That is, instead of comparing a local externally connected Tbolt Osc to the GPS, I want to compare it remotely to one of say Tom's supper H-masers  or Cs references.
> The single view Tbolt-Tic works great using averages of a half day plus to get down to 1e-13, but being nuts I want to do it Faster and better.
>
> Test setup:
> I have three COMPLETELY independent Tbolts running, each with its own LadyHeather monitor.
> Two of the Tbolts are a couple feet away from each other, the third one is a few hundred miles away.
> All three are in single satellite mode set to watch the same near overhead satellite.
> All three of these Tbolt oscillators are capable of short term noise a decade or two better than the short term GPS noise.
> I also measured the TBolt's engine phase noise to be a decade lower than the short term GPS noise.
> All three are in disable mode, so that their plotted LH phase noise is for the most part ALL due to the received satellite signal noise.
> My hope was that there would be a high correlation between the Phase noise of their three Phase plots..
> What I see is almost no correlation, they are all just doing their own thing with random phase noise of a couple ns.
> Just to check I tried the same test with a satellite that had an elevation of around 45 deg with the same results.
>
> One test I should run is to use the same antenna for two of the Tbolts,
> But that defeats the whole purpose, which is to be able to compare by way of LadyHeather's remote function, a local Osc to an external Rb or Cs remote reference Osc.
>
> Any suggestions?
> Something is wrong somewhere.
> Maybe it is that the Tbolt's engine noise is not what I measured it to be, but I have double checked that a couple of different ways.
> Anyone have personal common view experience comparing  Tbolts OR any other thing using GPS.
>
> ws
>
> *****************
>




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