[time-nuts] Z3805 two frequency maxima

[Bob Camp]

Hi

60 db isn't to bad a number. More or less:

100 ns -> 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation.  Still, pretty close.

Bob
  
On Nov 17, 2012, at 12:50 PM, Volker Esper <ailer2 at t-online.de> wrote:

> 
> So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading "5.000 MHz" - bingo!
> 
> May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc.
> 
> How would you have calculated the energy? What would be your ansatz?
> 
> Thanks so far
> 
> Volker
> 
> 
> Am 17.11.2012 17:55, schrieb Bob Camp:
>> Hi
>> 
>> That's what you get if you have "sub harmonic" energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805.  If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get.
>> 
>> Bob
>> 
>> On Nov 17, 2012, at 11:41 AM, Volker Esper<ailer2 at t-online.de>  wrote:
>> 
>>> Hi,
>>> 
>>> while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all:
>>> 
>>> The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps).
>>> 
>>> I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself.
>>> 
>>> So I plugged another oscillator, the reference TCXO of my signal generator (R&S SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum.
>>> 
>>> I havn't calculated the ADEV curve, yet.
>>> 
>>> See pictures.
>>> 
>>> Why does my GPSDO produce such a weird result?
>>> 
>>> Cheers
>>> 
>>> Volker - DF9PL
>>> <DSCF1437_bbb.jpg><DSCF1439_bbb.jpg>_______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
>> 
> 
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.