[time-nuts] Temperature weirdness with Thunderbolt & Lady Heather 5

Charles Steinmetz csteinmetz at yandex.com
Thu Dec 15 13:45:25 EST 2016

Tom wrote:

> There's something very odd going on here, either with Pete's TBolt, and/or with Mark's Heather v5.
> 2) It also shows some truly erratic behavior the last day and a half, with multiple, massive, sudden temperature drops going down several degrees. I've never seen this.

I think the more revealing trace is the DAC voltage.  There are ~70mV 
plunges, to a dead quiet (at this scale), more negative value.  70mV is 
huge, corresponding to a -35e-9 frequency shift (350mHz).  If the DAC 
voltage actually changed that much, it would pull the OCXO so far off 
frequency during these events that it would take much, much longer than 
shown (indeed, much longer than the width of these events) to 
re-stabilize.  Yet we see clean jumps within seconds, and no settling. 
(Unfortunately, the Tbolt's estimation of frequency is not plotted on 
the posted screen shot.)

I find it hard to believe that LH does much processing of the reported 
DAC voltage, so I think it's safe to say (1) the LH plot shows 
accurately what the Tbolt is reporting (at least WRT the DAC voltage), 
and (2) the actual DAC voltage is not doing what the Tbolt is reporting.

Looks like a sick Tbolt to me.

Best regards,


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