[time-nuts] Z3805 two frequency maxima

[Bob Camp]

Hi

A little more detail:

What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. 

Bob

 
On Nov 17, 2012, at 9:36 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
> 
> Just good old Fourier series. 
> 
> Bob
> 
> On Nov 17, 2012, at 9:12 PM, Volker Esper <ailer2 at t-online.de> wrote:
> 
>> 
>> I'm impressed - but what law is behind this?
>> 
>> 
>> Am 17.11.2012 21:26, schrieb 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
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>>>>> 
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>>>> 
>>>> 
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