[time-nuts] Hp 5060A C-field

[paul swed]

Tom and Corby
Thanks for the help. I suspect that the 5060/5061 is perhaps as good as it
can get.
My other references such as the 3801 and Tbolt have it down now in the
1X10-11 region. Close to 1 but goes above and below. I did find the magical
cfield R to be 70 ohms and will have to calculate the current.
When I do measurements for 10 ns displacement it takes some 13-18 minutes.
I also use a 5370b counter much easier to measure the ns drift than the
scope.
Regards
Paul
WB8TSL



On Fri, Jan 3, 2014 at 1:13 PM, Tom Van Baak (lab) <tvb at leapsecond.com>wrote:

> Hi Paul,
>
> About cesium clocks: hp 5060A and early versions of the hp 5061A needed to
> be able to keep *either* atomic time (true, accurate, stable, SI seconds)
> or astronomical time (inaccurate, unstable, slow, and gradually slowing,
> earth rotation time).
>
> The larger C-field range allowed this user choice of time-scales. I have
> many examples of both clocks here.
>
> It appears most time & frequency labs converted to "atomic time" in the
> late 60's and 70's which is why all later 5061A, all 5061B, every 5071A,
> and all modern atomic/ion/optical clocks tick "atomic" seconds instead of
> the slightly larger and monthly / seasonally / climatically / geologically
> / gravitationally variable "earth" seconds. And why we have leap seconds.
>
> In the past 50 years even die-hard astronomers have thrown in the towel
> and conceded that atomic time is a more stable time reference than earth
> rotation rate. In order to point modern, super-accurate telescopes they use
> a high-precision (sub-millisecond!) "DUT1" correction to convert
> physics-stable atomic time into engineering-accurate astronomical time;
> "close enough for government pointing work" as they say.
>
> Now that we're well into the post-astronomical time age, the narrow
> C-field range is adequate. If you have a 5060 or older 5061 there is no
> harm in using resistors to restrict the C-field range.
>
> /tvb (i5s)
>
> > On Jan 3, 2014, at 7:51 AM, paul swed <paulswedb at gmail.com> wrote:
> >
> > Corby
> > Having a good time tinkering with the 5061. Did change the resistors for
> > the cfield regulator so that its much close to the schematic and am
> > experimenting with that.
> > The system does seems to be able to be tuned through a stable position
> that
> > reduces the drift to 2 min/10ns drift and the CS is slow compared to the
> > 5065 RB set to loran C when its on the air.
> > I do have a older synth div board. No thumbwheel switches. It appears to
> me
> > to be jumpered at 8634. I think that may be wrong. The book says 2095 for
> > atomic time.
> > Appreciate your thoughts.
> > Regards
> > Paul
> >
> >
> >> On Thu, Jan 2, 2014 at 4:52 PM, paul swed <paulswedb at gmail.com> wrote:
> >>
> >> Corby
> >> I pulled the a15 board and there are no resistors, just a short across
> >> what would have been r19 and 21. So I suspect that there is to much
> current
> >> actually. Further speculation is that when the pot is toward ground more
> >> current flows from what I see in the schematic.
> >> I may guess that more current equals lower frequency?
> >> Regards
> >> Paul.
> >>
> >>
> >>> On Thu, Jan 2, 2014 at 4:22 PM, <cdelect at juno.com> wrote:
> >>>
> >>> Paul the C-field current is the same for the 5061A and 5060A.
> >>>
> >>> The 5060A C-field pot has LOTS more range than the later 5061A where
> they
> >>> installed resistors on each side of the pot to reduce the range.
> >>>
> >>> Corby
> >>>
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