[time-nuts] Re: DOXCO from Z3801

[Andy Talbot]

Ah, OK.    It's working great on just the inner one at the moment
The temp is unlikely to drop below 15 to 16C - shack room temperature worst
case winter nights.

Andy
www.g4jnt.com



On Wed, 7 Dec 2022 at 14:07, Bob kb8tq <kb8tq at n1k.org> wrote:

> 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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