[time-nuts] Re: Fixing PN degradation via ADEV measurement

[Bob kb8tq]

Hi

If the objective is “phase noise -130 dbc at a 10 KHz offset” and the signal is 
at 25 MHz, the resultant jitter ( in a 10 KHz bandwidth ) is likely in the < 500 fs 
range. The CNT-91 is only a 50 ps resolution device. 

Since it’s a counter, there is no practical way to vary the bandwidth. You get 
whatever the internal processing gives you. Even then, at 25 MHz a broadband
-130 dbc/Hz phase noise ( 10 MHz bandwidth) is still below 10 ps. Still below 
the counter’s floor. 

One of *many* calculators that let you play with jitter from phase noise:

https://rf-tools.com/jitter/ <https://rf-tools.com/jitter/>

It’s just the first one Mr Google turned up. There may be much better ones
out there. 

Bob

> On Jun 19, 2022, at 9:58 AM, Karen Tadevosyan <ra3apw at mail.ru> wrote:
> 
> Hi
> 
>> The CNT-91 has a very high noise floor if you are trying to “see” phase noise.
> 
> May be but with this Pendulum CNT-91 I can fix PN degradation in the range -130 ... -150 dBc/Hz where R&S FSQ8 can do nothing...
> 
> FYI: FSQ8 is not the worst SA: PN floor -130 dBc/Hz @10 kHz on 1 GHz.
> 
> Karen, ra3apw   
> 
> 
>