[time-nuts] OCXO Soft-Start

jimlux jimlux at earthlink.net
Wed Apr 12 23:18:38 EDT 2017

On 4/12/17 7:14 PM, Richard (Rick) Karlquist wrote:
> 10.9 MHz is likely the B-mode of the SC cut.
> (It's a different mode, not a different overtone).
> This mode has a tempco of 20 ppm and is used
> to do thermometry.
> IMHO, there is NO excuse for the oscillator
> designer to design an oscillator that doesn't
> oscillate unconditionally in the right mode.
> NONE!  What was the actual manufacturer of
> the OCXO? (AFAIK, Trimble doesn't make their
> own).
> My old boss at Zeta Labs (a really great boss)
> used to walk up to people who were testing
> their latest circuit and momentarily turn
> down the current limit on each of the power
> supplies to see if the circuit recovered
> correctly.  It often didn't, and then it
> was back to the drawing board...

These days, a common trap is when you've got a DC/DC converter on the 
input - with a soft start, the current goes huge, causing all kinds of 

(I'm in the middle of closing a failure report on just such a 
sensitivity - an unexpected interaction between the source DC/DC 
converter and the load DC/DC converter..)

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