[time-nuts] Ebay FE-5680A Rb: Are they that good?

Peter Bell bell.peter at gmail.com
Thu Dec 8 20:27:31 EST 2011

The short answer is that there are several different versions of the
"FE-5880A" around, but most of the ones that are currently available
at low cost are the ones with "FEI P/N 217400-30352-1" on them.  The
significant characteristics of these specific units are:

1) They need a 5V supply on pin 4 of the D-type connector - none of
the other FE-5680As I've seen need this.
2) The output frequency is 10MHz, and is derived by dividing down the
internal 60MHz oscillator - these units do not have a programmable DDS
on the output, so if you were thinking of programming them to generate
some arbitrary frequency then you need to get a different version.
3) Although there is a fine frequency adjust pot on the board, it
doesn't appear to do anything - I have checked this with 5 of these
units, and they are all the same, so it doesn't look like a fault,
it's just the way they are.
4) They do have the "Opt-02" frequency trim on the RS-232 interface,
and it works as described - note that the trim range is only a few
hundred Hz either side of the nominal 10MHz frequency.
5) Although the output is a sine wave, it's not especially nice -
internally it's derived from a square wave fed into a rather simple
filter circuit - having said that, none of my test gear has any
problem with using it for a reference input,



On Fri, Dec 9, 2011 at 3:53 AM, Chris Albertson
<albertson.chris at gmail.com> wrote:
> On Thu, Dec 8, 2011 at 10:58 AM, Chuck Forsberg WA7KGX N2469R
> <caf at omen.com> wrote:
>> FE-5680A Rubidium Atomic Frequency Standard Oscillator Transceivers 10Mhz
>> Out
> There was a lot of email about these a short while ago.  But is is
> still not clear to me if these are even adjustable and if not, how far
> have they drifted off of 10Mhz since they were new.    I'd like to buy
> one and calibrate it to a GPS.
> Chris Albertson
> Redondo Beach, California
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