[time-nuts] 5370B OCXO

John Miles jmiles at pop.net
Fri Mar 12 03:43:07 UTC 2010


Many if not most 5370-based measurements are based on differential timing
between the START and STOP channels, and wouldn't benefit from a better 10
MHz reference.  If a customer did need something better, they probably
already had a house standard to pipe in the back... and if not, HP would
have been able to sell them one.  It made more sense to keep the cost down
by not including a high-end OCXO that would have gone unappreciated by most
users.

The 5370's jitter+resolution floor doesn't allow it to reach 1E-11 at t=1s
in any event, so the -60111 wouldn't have been the limiting factor in the
short term.

One valid question, though, is why they bothered to put the nicer
10811-60109 OCXOs in the post-2120 series 5065A models, where its short-term
performance is hosed by tying it to the rubidium reference with a ~1 Hz
loop.  Those 5065As would have been OK with a -60111, at least in the
pre-2632 serial #s with the original integrator board.  I'd be curious to
know if they lowered the loop BW when they respun the integrator PCB.

-- john, KE5FX


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Bob Camp
> Sent: Thursday, March 11, 2010 7:11 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] 5370B OCXO
>
>
> Hi
>
> The OCXO in the 5370B is a 10811-60111. The only added spec on it
> is a 1x10^-11 ADEV spec at 1 second. By modern standards that's
> not a real tight spec. There are other 10811's with tighter specs
> on them at 1 second. My guess is that it was not a real tight
> spec for the 10811 to hit.
>
> The short term would appear to contribute to the total error on
> the counter. Why not put a better oscillator in it?
>
> Bob
>
>
>
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