[time-nuts] "The Penultimate HP5065 A15"

[Bob kb8tq]

Hi


> On Aug 4, 2020, at 3:50 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> --------
> Bob kb8tq writes:
> 
>>> I have not given much thought to A11 yet, and I do find a certain
>>> elegance in the wien-bridge approach.  It is worth noting that the
>>> actual heaters run of the unregulated supply, when I stabilized
>>> that, A11 worked less hard.
>> 
>> The AC bridge approach certainly worked well 'back in the day'.
> 
> Actually, what I like is that it makes it possible to decide the
> frequency spectrum of the inevitable noise, and in this case put
> it up around a kilohertz where it is a lot less likely to cause
> trouble.
> 
> The "modern" approach to that is to modulate or dither with a
> good long PRNG to whiten the noise, and while good in theory,
> it is not _that_ easy to get right in practice.

Of course one could simply cave in to the fact that for the sort of
gain required here, a pure DC controller works quite well.

I know - that takes all the fun out of it …..

Bob


> 
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.