[time-nuts] Trimble Tbolt temperature

[Charles Steinmetz]

Tom wrote:

> Section 5.1.2 (Kalman Filtering) on page 5-4 (PDF page 48) says:
>
> Oscillator performance is subject to two basic effects. First, changes
> in environmental temperature can cause the oscillator to speed up to
> slow down. Second, the oscillator has a natural tendency to drift over
> time. This is called aging.
>
> Both temperature and aging can be mathematically predicted. However, the
> characteristics vary from crystal to crystal. The Kalman filtering
> monitors the unique oscillator performance over time and temperature and
> records this behavior.

The DS1620, perched way over in the corner of the board, cannot provide 
useful crystal temperature data, even by inference.  That would need to 
come from within the oven at the very least, more likely from inside the 
crystal envelope itself using, e.g., an IR thermometer.

Instead, Kalman filters in GPSDOs track the oscillator frequency 
continuously and do their best to separate the drift effects from the 
temperature effects using software algorithms (note "mathematically 
predicted" in the paragraph above).  You can see a hint of this by 
monitoring the statistics from one of the older HP units like a Z3801.

Best regards,

Charles