[time-nuts] Question for my new GPSDO

[Jim Harman]

On Tue, Oct 15, 2019 at 10:00 PM Hal Murray <hmurray at megapathdsl.net> wrote:

>
>
> You can get a few bits by reducing the tuning range.  Suppose you follow
> the
> DAC with an OpAmp with a gain of 1/8 while the reference is adjustable.
> That
> adds 3 bits of resolution by decreasing the output range.  The downside is
> that you have to manually set the adjustment.
>
>
> Jim says:
That's true, but why not just a resistor bias network rather than an op
amp?

>
> How big a box of whatever do I need to get the thermal time constant large
> relative to 100 or 1000 seconds?
>
> Jim says:
It's not the size of the box that matters but what's in it. You want to
have enough thermal mass to reduce temperature fluctuations when sun shines
on the box or you open the window, while minimizing air currents near the
oven and allowing enough thermal conduction to prevent the system from
overheating.

My GPSDO dissipates about 3 watts and I have had good results by putting
the system in a small picnic cooler along with 3 one liter bottles of water
and some bubble-wrap to fill up the extra space.
-- 

--Jim Harman