[time-nuts] antennas

Hal Murray hmurray at megapathdsl.net
Tue Sep 28 07:38:31 UTC 2010

> What is the purpose of the temperature sensor chip on the PCB, anyway? Isn't
> the temperature inside the OCXO much more important? 

The OCXO isn't perfcet.  The frequency will shift slightly with environmental 
temperature changes.

It may have been more important without the high-quality OCXO option that 
many recent TBolts seem to have.

Here is some data:


It's 24 hours of data in my non air-conditioned spare room.

I shifted the DAC voltage to be close to zero.

The spikes on the red graph are recovering from holdover.  (The antenna isn't 
very good.)

The slight eye openings are hysteresis.

Does anybody know if they calibrate it on the fly or do it once at 
manufacturing checkout?  (or just wire a constant into the source code?)

Trying to do it do it on the fly seems hard if your system is running in a 
well air-conditioned place where you don't get much temperature swing.

These are my opinions, not necessarily my employer's.  I hate spam.

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