[time-nuts] RFTG-m-RB

[Bruce Griffiths]

James R. Gorr wrote:
> What I am trying to accomplish is provide a reference
> for my HP 3586C.  I want to try my hand at the FMT in
> February.
>
> I have a set of the Lucent RFTG-m-XO and RFTG-m-RB.
>
> My options are use the RB as stand alone or use the XO
> with the GPS, or combine the two.  (I believe I have
> the "matched set" that should work together).
>
> Either way, they both output 15 MHz sine wave and the
> RB outputs 10 MHz square wave.
>
> Is there an advantage using one over the other?  I
> would like to set them up together as the matched set
> they are supposed to be, although I don't think there
> is any advantage to that for me really.
>
> So, for starters I was just going to use the Rb's 10
> MHz output.  But the more I think about it, the more
> questions I have.
>
> >From reading all the previous posts about these the
> GPS does not disciplines the Rb.  The Rb unit is there
> to take over in the even the GPS fails.  So that leads
> me to believe that the XO is more accurate in the
> short term as long as it has something to steer it
> like a GPS or the Rb.  
>
> So my guess is that the XO would really be a better
> choice, but I am back to dividing the 15 MHz down to
> 10 MHz.  I understand about dividing by 3 and
> multiplying by 2.  Could someone please provide a
> circuit?
>
> Am I right in my logic and am I going down the right
> path with my project?
>
> Thanks for all the expert support.  
>
> Jamie
>
>   
Dividing by 3 and then multiplying by 2 is not necessary, it just adds
complexity and noise.

Just use a pair of JK flipflops (no external gates required to divide by
3 unlike when using D flipflops) configured to divide by 3 and extract
the 10MHz component in the divider output.
For one version of a JK fliflop divide by 3 circuit see:
http://www.play-hookey.com/digital/frequency_dividers.html

To extract the desired 10MHz component from the divider output see the
square to sine section of:
http://www.wenzel.com/documents/waveform.html

Just adjust the output LC filter to extract the desired 10MHz component.

If you are really worried about noise use a regenerative divider
configured to divide by 3.
Both f/3 (5MHz) and 2f/3 (10MHz) signals are used in the divider
feedback loop.
However your source probably doesn't warrant the complexity and cost of
such a regenerative divider.


Bruce