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

[wb6bnq]

Hi Pete,

Are you really at an altitude of 645 meters ?

Also, it seems that your oscillator gain (currently at -5 Hz/v) may not 
be set right ?

Have you checked the power supply voltages and observed them on an 
oscilloscope to see if they are relatively clean and free of spurious junk ?

The available number of SATS  is quite low and could be a matter of concern.

Bill....WB6BNQ


Pete Stephenson wrote:

>On 12/15/2016 7:45 PM, Charles Steinmetz wrote:
>  
>
>>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.)
>>    
>>
>
>Apologies, I did have the frequency plot turned off. I've taken some
>more screenshots with the frequency plot turned on.
>
>screenshot.png is a close-up of one of the odd spikes, while
>screenshot2.png took place ~10 minutes later (I just scrolled to the right).
>
>The small frequency jumps in screenshot2.png are due to satellites
>entering and leaving the field of view. Due to the setup of my
>apartment, the antenna location is decidedly sub-optimal and has a clear
>view only to the northwest.
>
>  
>
>>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.
>>    
>>
>
>Any idea what might be the issue? I can do SMT rework to replace a bad
>temperature sensor or other faulty chips, within reason (super-fine
>pitch stuff is a pain).
>
>Cheers!
>-Pete
>
>  
>
>>Best regards,
>>
>>Charles
>>
>>
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>>    
>>
>
>  
>
>
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