[time-nuts] Opening an Isotemp OCXO

jimlux jimlux at earthlink.net
Fri Oct 28 17:59:10 EDT 2016

On 10/28/16 1:09 PM, Bob Stewart wrote:
> Hi Bob,
> Can't the OCXOs be characterized pretty closely by someone with the right tools and staff?  I don't have a big sample to speak from, but the Trimbles I use only have a couple of ceramic coated pieces, and those can be exposed down to the die by hand and then characterized, can't they?  Granted, that's beyond my capabilities, but given the right tools and employees...

The real thing is "which requirement do I really, really care about" 
beyond the straightforward frequency stability/phase noise specs.

You might have a specific "I care about 1 Hz to 100 Hz, but don't much 
are about >100 Hz or <1Hz" and you're willing to let the mfr do pretty 
much anything else for the rest.

I recently had a requirement where I don't much care about absolute 
frequency accuracy, but I do care about phase noise and short term (<3 
seconds) stability.  We got some quotes for OCXOs with the oven 
disabled, figuring that we don't need to burn the power for the oven, 
since that's more about frequency accuracy, and our environment (in 
space) doesn't vary more than a couple degrees over hours.  That's 
something you'll never see in a catalog.

We buy oscillators at JPL for things like landing radars - the operating 
life is minutes, but it had better work for those minutes - we care not 
what the aging or frequency accuracy is in this situation.

I know people that have bought parts for telemetry transmitters on 
devices with life measured in seconds - there, the critical requirement 
was "must start from -80C and run for 10 seconds"

A coworker was telling me about requirements for oscillators in fire 
control radars attached to gatling guns - Now there's a vibe sensitivity 

So, as Bob pointed out, most oscillators go into applications that have 
idiosyncratic requirements and a cost or delivery schedule requirement 
pushing against the overall performance requirement.  Not everyone wants 
a 1kg ultra stable oscillator from APL with a 3 year delivery time.

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