jmiles@pop.net said:

The PRS-10 has a huge spur at 60 Hz.

What were you using for a power supply?  (Or what should I be asking?)

--
These are my opinions.  I hate spam.

Magnus warned us about the use of very long time constant to act on
disciplining. In my opinion it is better to use quieter data coming from a
relatively fast sampling Kalman filter and correct as frequently as
possible then train the filter with long time constants.

On Fri, Aug 24, 2012 at 9:14 AM, Hal Murray hmurray@megapathdsl.net wrote:

I turned off the spur display for that plot, to reduce the visual clutter.
But especially when several spurs are clustered together, TimeLab can fail
to detect some of them, and any spurs that aren't detected can't be removed.
There are actually three spurs near 60 Hz in that plot, two of which were
detected and one of which was missed (the one you saw.)  One of those will
likely be an AC line spur, while the other two are of unknown origin.
(Here's the same plot with spur amplitudes plotted.)

The PRS10's spur specification is -130 dBc, so these would be pretty close
to the spec.  -130 dBc is not a very strong spur, in the grand scheme of
things.  I wouldn't want to see an OCXO with a non-line-related spur at
-130 dBc, but anything as complex as a rubidium standard will probably have
a few spurs of that magnitude here and there.

As far as line-related spurs go, no attempt was made to minimize ground
loops between the PRS10 and the reference, their power supplies, the PC, or
anything else, so I wouldn't worry about them in this case.

-- john, KE5FX
www.miles.io

On 08/24/2012 11:35 AM, Azelio Boriani wrote:

It really, really depends. I usually warn about using too long time
constants. As John has correctly pointed out, the PRS-10 has a good
crystal oscillator in it, allowing for longer time-constants to be used.

There are many benefits of using an SC-cut crystal oven in a rubidium.

I also agree with John about the hump, its bound to be there due to the
PLL action. There are two sources of humpiness at the cross-over. The
first is that at the cross-over you transition from the low-pass
filtered reference noise and the high-pass filtered oscillator and loop
noise. Since the noises is uncorrelated, their powers will add. The
cross-over filter does not suppress one noise before the other kicks in
to sufficient degree of suppressing the additive effect. Another aspect
is that the PLL Q-value creates a gain at the cross-over point, and
using too low Q values acts like an equalizer to bring noise up.

This is to be expected and comes out of standard control system math.

Cheers,
Magnus

OK, so speeding up the disciplining will shift the hump on the left and
rise it, while slowing down will shift to the right and lower it.

On Sat, Aug 25, 2012 at 1:31 PM, Magnus Danielson <
magnus@rubidium.dyndns.org> wrote:

Hi

…… and picking the cross over point based on noise plots of the sources on both sides of the detector will give you the optimum point.

Bob

On Aug 25, 2012, at 8:10 AM, Azelio Boriani azelio.boriani@screen.it wrote:

It seems by collecting data while changing the loop time that hump or
knee could be mathematically removed, which with good quartz could be the
beginning of a very serious standard.

Thomas Knox

It seems by collecting data while changing the loop time that hump or knee could be mathematically removed, which with good quartz could be a beginning of a very serious standard.

Hi

Since you are dealing with two sources, both with random noise on them, there's no "easy" way to mathematically remove it.

Bob

On Aug 25, 2012, at 1:02 PM, Tom Knox actast@hotmail.com wrote:

On Sat, Aug 25, 2012 at 11:41:21AM -0700, J. Forster wrote:

I have the whole working PRR-10 system including 2 Rbs and AFAIK

that PCB just contains redundant power and provisions for passing a
couple of status bits from the RB (lock I think)... if you have a PRR-10
system it would be useful, but I'm not sure it is otherwise.

Possible there is a -48 volt input DC to DC converter... if it

would be useful I go go look at one of mine to refresh my memory.

The heat sink is useful with the LPRO RB of course.

I assume you bought it for the LPRO...

You may not be aware, but the system is designed to use a DDS to

offset the frequency of a free running 10 MHz source to make it accurate
based on GPS timing ... so the Rb is not disciplined with its C field or
similar - it is free running.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."