[time-nuts] HP5065A C-field current voltage mod

[John Miles]

One idea would be to leave the existing C-field circuit in place with a switch to disable it.  That'd preserve your ability to carry out the second harmonic adjustment procedure, while allowing you to switch back to a stable current for normal operation.

For that matter, it's not clear what "aging process in the A12 RVFR assembly" accounts for the presence of that adjustment procedure in the manual.  Given the absence of any other aging mechanisms other than (very) gradual lamp darkening, I have to wonder if the Implementers mistakenly blamed the RVFR for drift in some other component.  I suppose they could be referring to partial diffusion of the buffer gas through the cell walls... but after 40 years, is there any indication that this is actually an issue?

Has anyone looked into the oven temperature stability to make sure that further optimization of C-field stability is worthwhile?  I'm a bit behind on my email so this may have already come up.

-- john, KE5FX
Miles Design LLC


> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Poul-
> Henning Kamp
> Sent: Friday, September 04, 2015 2:38 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] HP5065A C-field current voltage mod
> 
> --------
> In message <89828.1441376015 at critter.freebsd.dk>, "Poul-Henning Kamp"
> writes:
> 
> >I actually have some calculations relevant to this, I'll write them
> >up on my homepage when I have a second.
> 
> Here:
> 
> 	http://phk.freebsd.dk/hacks/HP5065A/20150904_math
> 
> I'd be very pleased if somebody would double-check the calculations.
> 
> --
> 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.
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