[time-nuts] FE-5680A Results so far

Said Jackson saidjack at aol.com
Thu Dec 29 13:37:14 EST 2011

Hello Mike,

We measured a couple of these 5680As on a tsc5125a analyzer. With different quality supplies.

Very noisy buggers, huge number of spurs and very high noise floor -130dBc or so if I recall correctly. Thats probably the jitter you are seeing. Probably due to the dds generating the output not a crystal.

ADEV was parts in E-011 while good, not very good.

Frequency accuracy was +5E-010 then tap the box hard and it goes to -1ppb.

Good enough as a portable frequency counter reference, as the offset can be compensated, and the output is fairly stable...

These units could really use gps disciplining and a crystal post filter.

Great stuff for $40, new they must have been over $1000.


On Dec 29, 2011, at 1:14, mike cook <michael.cook at sfr.fr> wrote:

> Hi,
> Just got my cheapo 5680A.  It was accompanied by a little teddy bear clutching a L7805CV !
> Got a couple of questions.
> 1) What is the expected 10MHz peak to peak voltage.  FEI doc seems to indicate 0,5V but I am getting only 200mv.
> 2) What is the sensitivity to 15V input level. I am only measuring 14,722 (stable) on Pin1.
> 3) Could this low input voltage affect output voltage?
> The box locks after a couple of minutes but my TDS 210 is showing a very jittery  ( 9,98-10,02 MHz ) but well formed sine wave for 8 hours of being powered on.  Could this also be an artefact of low main power?
> rega
> Mike
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