[time-nuts] HP5065A C-field mods and optical unit mods --> OFF LIST !!!
kb8tq at n1k.org
Thu Nov 16 16:13:48 EST 2017
So, when do they go up for sale? :)
( = If and when they do, I’m still shopping for one)
> On Nov 16, 2017, at 3:58 PM, <cdelect at juno.com> <cdelect at juno.com> wrote:
> HP5065A C-field mods and optical unit mods
> In addition to the power supply mods:
> -removed AC components
> -power now supplied with an external DC lab grade low noise
> highly regulated supply.
> -temperature coefficient of +20 Volt supply adjusted to be
> below 1PPM/deg C
> See: https://www.febo.com/pipermail/time-nuts/2017-August/106634.html
> I've now installed the improved C-field circuit that has
> less than +- 1PPM variation per degree C.
> The optical unit has been installed into a sealed enclosure
> that has been purged with dry Nitrogen. This eliminates
> any Barometric pressure effects and also eliminates
> drift caused by Helium permeation.
> Tests at this point show a very nice long term stability.
> Last mod will use a small PC closed loop liquid cooler to
> keep the outside of the sealed enclosure at a constant temperature
> essentially making it a double oven.
> I'm also working on:
> An active temp compensation scheme to add to the
> active barometric compensation I outlined earlier.
> See: https://www.febo.com/pipermail/time-nuts/2016-May/097829.html
> And a passive optical unit temperature compensation using a
> PIX shows the sealed optical unit installed into a slightly taller
> chassis. (The 5065C ?)
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