Hi Chris,

The short answer is NO !

Bill....WB6BNQ

chris 0 wrote:

What would you intend to do with the signal?

I'm not a microwave expert, but I believe the only microwave signals in the FE-5680A are the output of the step-recovery diode that multiplies the 60 MHz VCXO signal up to the 114th harmonic, plus that mixed with the 5.313 MHz DDS output to reach the Rb frequency. ( 114 * 60 Mhz - 5.313 Mhz -> 6.835 Ghz)  The SRD output would be just a mix of a lot of harmonics, not any sort of clean signal; I suspect the only real filter is the resonant cavity which is occupied by the Rb bulb.  I suppose a small enough probe into that cavity might not detune it too much, but you'd probably need an additional amplifier to do anything with that signal.  Iin this device the Rb vapor itself does not generate microwaves (like an active H maser), it just absorbs them, and it changes optically if the signal happens to be at the resonance frequency around 6.8 GHz.

Hi

Simple answer is don't bother.

More complex answer - of course you can. You will get a forest of spikes (every 5, MHz or so ).

Bob

On Jan 30, 2012, at 6:26 PM, chris 0 viscousplacebo@gmail.com wrote:

On 31/01/12 02:20, Bob Camp wrote:

Also, since the 5,3 MHz is modulated, 1,4 kHz apart is the two signals,
and then a skirt of side-bands as the frequency modulation is relatively
quick.

It's not clean.

BTW. A fun hack would be to hook up the 63,8976 MHz OCXO in replacement
of the 60 MHz and then re-adjusting the DDS to 2.35645 MHz, as the 107s
overtone of the OCXO minus the new DDS frequency hits the Rb resonance.

Cheers,
Magnus

If I understand your question right...

Most rubidium frequency standards (and cesium for that matter)
do not actually output that frequency. I know in the popular press
they talk about the "precise vibrations of the cesium atom" or the
"precise frequency that they emit" but that's a metaphor and not
how they actually work. The atoms don't vibrate, they don't emit
a GHz frequency, and you don't count 9,192,631,770 of them to
make one second.

What typically happens is that electronics synthesizes an RF
(microwave) signal and continuously sweeps across a narrow
range of frequencies; the element (Rb or Cs or H) will respond
more or less depending on how correct the probe frequency is.
A servo then tries to keep the probe frequency centered on the
peak. These are all called "passive" standards.

The rare exception is the "active" hydrogen maser; where there
really is a live signal (1420+ MHz) coming out of the apparatus.

You may find these two papers helpful:

Introduction to time and frequency metrology
http://tf.nist.gov/general/pdf/1288.pdf

Fundamentals of Time and Frequency
http://tf.nist.gov/general/pdf/1498.pdf

/tvb

El 31/01/2012 02:52, Magnus Danielson escribió:

And then we will have a not less fun 10.6469MHz and 0.939Hz outputs :)
However, if the DDS can easily be reprogrammed to large offsets (and the
output filter is a simple lowpass...), that idea is very useful if you
need an strange frequency and have an OCXO at 6x that extrange frequency ;)

Regards,

Javier

On 31/01/12 07:27, Javier Herrero wrote:

We seems to get those OCXOs alongside anyway, so I was just toying with
the idea to see what kind of performance that would give us. A quieter
OCXO. For more ordinary frequency output, an additional DDS like the
original 5680 would be nice.

Cheers,
Magnus