[time-nuts] Thunderbolt mounting

[Mark Sims]

I tried putting a Tbolt in a small (six-pack sized) Coleman cooler.   The temperature rose above the alarm temperature...  it does not take much insulation to cause problems.

Lady Heather's built in temperature PID controller works very well.   When properly set it up,  short term variations can be well under 20 millidegrees.   Long term RMS temperature error can be a few microdegrees or less.   Attached is a screen dump showing a 0 microdegree RMS temp error over 72 hours!

Besides the TT command to set the desired setpoint temperature,  there are some built in PID parameter commands (KW sets a slow pid,    KM sets a fast pid,  KA attempts a PID autotune...  you can also tweak the various PID parameters individually...  see the routine edit_pid_value() in heathui.cpp for some idea of the available parameters).   

For best performance,  it helps to have the power supply in the temperature controlled box.  This will minimize the effects of temperature variation on the supply,  which can be a third of the overall system temperature sensitivity.   It is also a good idea to not have the box so well sealed that the unit overheats if the computer/PID/fan shuts down.  You probably don't want a flammable box in case your cheapo Chinese power supply bursts into flame.

For best operation of a new Tbolt,  you should first run the 48 hour precision survey,  then execute the &a auto-tune command.  Autotune sets the oscillator parameters,  elevation mask,  and signal level mask to time-nutty values.  Before running &a,  first set the elevation mask to a low value and collect data for a couple of hours.   This lets the program find the satellite elevation angle where the signal starts to degrade.

Note that it can take several weeks for an old, unused oscillator to fully stabilize and age in.

 		 	   		  
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