[time-nuts] "The Penultimate HP5065 A15"

[Magnus Danielson]

Hi Poul-Henning,

On 2020-08-04 00:32, Poul-Henning Kamp wrote:
> --------
> Attila Kinali writes:
>
>>> The main reason I dont just repair/replace the A15 is that 
>>> I want to find out how much instability the PSU contributes.
>> There are very few points where supply voltage (in)stability
>> contributes to long term frequency drift in a Rb vapor cell standard.
> Obviously.
>
> But it does contribute quite a lot on the sub-hour time-scale, some
> of it via temperature-dependencies.

If that is the range you aim to improve, then I strongly recommend you
do re-read the postings I did about phase noise in detector range, as I
have showed that phase-noise get's mixed down to DC and increase the
noise there. With very ugly and hand-wavey hack I was able to
significantly reduce that noise essentially by cleaning up the
phase-noise. Just as Corby's filter trick, which also aims to reduce
noise, one need to figure out the dominant noise sources, then reduce
them from the top candidate and then down. I have not seen your efforts
include the oscillator phase-noise consideration. With that I'm not
saying that you attempts is wrong, rather, maybe not the first thing
that I would start with.

I will pursue my phase-noise approach until I see diminishing returns
there, and then look to see what could be the next dominant noise
contribution. In this regard I do not see Corbys or your approaches as
lost, but rather very interesting, as I come to that point.

> > I would go for the LTZ1000 if you can. The LM399 has gone out of
>> fashion for a reason: [...]
> Yes, I know, being also a volt-nut :-)

I have not yet jumped down that rabbit-hole as I am by far not done with
the current one. :)

I've been looking at the LTZ1000 and one day I may get some.

Cheers,
Magnus