[time-nuts] Re: DOXCO from Z3801

[Bob kb8tq]

Hi

Will your lab be running below freezing? If not, just ignore the outer heater and move on. 
The main reason that heater exists is a very early requirement to have the reference operate
at (and quickly warm up from)  -40C. The cell guys pretty much gave up on that idea after they 
dug into all of the grubby details of the rest of the gear. 

Bob

> On Dec 7, 2022, at 4:38 AM, Andy Talbot via time-nuts <time-nuts at lists.febo.com> wrote:
> 
>> I've been given a defunct Z3801 with a fully working ovened oscillator.
>> The rest of the GPSDO circuitry is just junk and will be chucked, but I
>> want to get the DOXCO running as a backup high stability reference here.
>> 
>> I've worked out the power connections for the oscillator and inner oven,
>> and have powered it up with +12V & +24V supplies.   It's currently just
>> warmed up and is happily generating a nice sine at 10MHz, with +0.3V (at
>> the moment) t on the EFC.
>> 
>> I applied 24V to the outer oven earlier to see what happened, and measured
>> the thermistor resistance as it warmed, watching it fall from 110kΩat room
>> temp to 30kΩ where I stopped.  I know the controller for the outer oven is
>> in external circuitry, but a brief web search failed to show a) what
>> temperature it should run at, To, and b) what the thermistor resistance
>> would be at that temperature, Ro.
>> 
>> Does anyone here know these figures off hand, or do I need to go to the
>> web and download the circuit and trace out the outer oven controller
>> details.   I'll be doing my own controller circuitry, so just need To and
>> Ro.
>> 
>> Andy
>> www.g4jnt.com
>> 
>> 
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