[time-nuts] FE-5680B Rubidium and DDS

Clint Jay cjaysharp at gmail.com
Sat Sep 26 02:36:30 EDT 2015


Bryan, I also found a stable 30MHz which I think is used to clock the
optional DDS board so I intend to experiment adding an AD9851 board with 6x
multiplier enabled but first I want to try and understand why the unit
locks and only outputs 10MHz from the XC9572, something in the firmware
appears to turn off the output, I may get around to experimenting a little
more soon and will of course share my findings if they're of interest. .

Bob, there are files which claim to be a dump of the firmware and also the
XC9572 along with a partial schematic but they're from a 5680A which, from
the pictures on the net, is a slightly different hardware version although
the major components appear identical so it may be possible to modify the B
version Bryan and I have.

On 26 September 2015 at 02:45, Bryan _ <bpl521 at outlook.com> wrote:

> There is information on this thread on how you can tap into the unit at
> various points to get 20 and 60Mhz. Other owners have used a divider to
> bring it to the 10Mhz frequency desired. I have one of these units and
> haven't gone around to dividing it down. I purchased mine from Ebay and the
> seller notes that this particular version will output 10Mhz for a second or
> two and then disappear. I suspect you have the same version, maybe even the
> same seller, so the operation of these particular units appears to be
> normal. Mine will lock so I know it's working.
>
> http://www.eevblog.com/forum/testgear/fe-5680b-1pps-to-10mhz/msg556800/#msg556800
> I as well wish there was a quick way of converting it back to 10Mhz. I am
> sure it can be done, just not sure how or where to look <g>
>
> -=Bryan=-
>
> > From: kb8tq at n1k.org
> > Date: Fri, 25 Sep 2015 17:45:08 -0400
> > To: time-nuts at febo.com
> > Subject: Re: [time-nuts] FE-5680B Rubidium and DDS
> >
> > Hi
> >
> > There is no dump of the firmware. The problem you are most likely
> > having is not firmware related.
> >
> > If the VCXO i the unit drifts to far it needs to be re-tuned. Until this
> is done
> > the device simply sits in a “search for lock” loop forever and ever.
> >
> > Simple way to do it:
> >
> > Monitor the VCXO and bump the trimmer until the frequency goes above the
> intended
> > target (10 x N MHz depending on your monitor point) by at least 0.15
> ppm. The sweep is
> > slow enough that a counter running at a 0.1 second gate will easily show
> you what’s going on.
> >
> > Of course it can be other things. All of them are a bit more involved to
> fix.
> >
> > Bob
> >
> > > On Sep 25, 2015, at 11:34 AM, Clint Jay <cjaysharp at gmail.com> wrote:
> > >
> > > I've recently purchased one of the PPS Only FE Rubidium standards from
> eBay
> > > and, like many others I suspect, haven't been able to get a stable
> output
> > > frequency that lasts longer than a few seconds from the module.
> > >
> > > It appears that the 10MHz source vanishes after a few seconds but this
> is
> > > controlled by firmware.
> > >
> > > Which leads to my question, there is a dump of the firmware from the
> > > FE-5680, has anyone tried to reprogram one?
> > > --
> > > Clint.
> > >
> > > *No trees were harmed in the sending of this mail. However, a large
> number
> > > of electrons were greatly inconvenienced.*
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-- 
Clint.

*No trees were harmed in the sending of this mail. However, a large number
of electrons were greatly inconvenienced.*


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