[time-nuts] FE-5680A Question

[Bob Camp]

Hi

The sweep range on the LPRO's is very similar to the sweep range on the
FE's. They both run the VCXO over a very wide range compared to the width of
the Rb resonance. They both also have to accommodate VCXO temperature
performance and aging. 

Bob


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chris Albertson
Sent: Wednesday, February 15, 2012 5:34 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE-5680A Question

On Wed, Feb 15, 2012 at 2:17 PM, Bob Camp <lists at rtty.us> wrote:
> Hi
>
> If you look at an LPRO or FRS or any of the other brands of Rb's their
sweep
> is very different. They don't spend very much time at the ends of the
sweep
> at all. It's pretty much a triangle wave sweep up and back sort of thing.
> They don't seem to care weather they catch the lock going high to low or
> going low to high. The rate of the sweep is *much* slower than what FE is
> doing on these units. Since there isn't a "brain" in most of them, there's
> no pattern watching stuff there. They just look for a lock signal
(amplitude
> out of the detector) and stop sweeping when they see it.

That method requires that your sweep in so narrow that it can't catch
any other adjacent spectral lines or "dips" in the light.   FEI may
have found a way to use a much wider sweep by havinf a "brain" able to
know the fauslt dips from the one it wants.

The "ends" that appear dead might be where the software analyses the
data from the previous sweep.  I doubt the little uP can mulitask.
The uP is doing "something" when it is not sending commands to the DDS
to cause the sweep.  My understanding of a Rb physics package is that
you get a "forest" of lines and only the one is the "good" one.

Chris Albertson
Redondo Beach, California

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