[time-nuts] HP5065A C-field mods and optical unit mods --> OFF LIST !!!
Bob kb8tq
kb8tq at n1k.org
Thu Nov 16 21:13:48 UTC 2017
Hi
So, when do they go up for sale? :)
( = If and when they do, I’m still shopping for one)
Bob
> 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
> thermistor/resistor
> arrangement.
>
> PIX shows the sealed optical unit installed into a slightly taller
> chassis. (The 5065C ?)
>
> Cheers!
>
> Corby<5065crs.jpg>_______________________________________________
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