[time-nuts] Low-pass Filter for 5 and 10 MHz

[Volker Esper]

...but what about the phase jitter of the filter itself? While absolute 
phase shift may not (or may?) be an issue I guess that passive filters 
do have a phase jitter, too, due to mechanical vibration, tempco, and 
what else.

Particularly at frequencies where the filter response has sharp slopes 
(resonance or corner frequency) the phase variation (d phi / d f) is 
quite big. Thus small frequency changes lead to considerable phase shift 
variation what in turn should lead to phase jitter added to our holy 
signal - what about overall ADEV?

Wouldn't it be better to not filter the 10 MHz signal when used solely 
as a frequency standard?

I understand, that a high Q filter in a PLL reduces the phase noise of 
that oscillator - until the jitter of the filter becomes important. Am I 
wrong?

Volker


Am 12.04.2013 02:31, schrieb Richard (Rick) Karlquist:
> Actually, the opposite is true.  Notches have the least phase
> shift at the frequency being passed, which is what matters.
> It is true that the phase shift at the notch frequency is
> uncontrolled, but that is not important.  The HP8662A
> had an interesting PLL synthesizer where they had 10 notch
> filters for the first 10 harmonics of the sampling frequencies.
> This minimized phase shift within the loop bandwidth that
> detracted from phase margin.  I designers of the 8662
> definitely know what they were doing.
>
> Rick Karlquist N6RK
>
> On 4/11/2013 5:02 PM, Alan Melia wrote:
>> Maybe a silly question but isnt the phase response of the filter
>> important in this application ?? notches have fairly vicious phase 
>> shifts.
>>
>> Alan
>> G3NYK
>> ----- Original Message ----- From: "Luciano Paramithiotti"
>> <timeok.it at gmail.com>
>> To: <time-nuts at febo.com>
>> Sent: Thursday, April 11, 2013 5:42 PM
>> Subject: [time-nuts] Low-pass Filter for 5 and 10 MHz
>>
>>
>>> A simple low pass filter to cut second and third harmonics from a 5 
>>> or 10
>>> MHZ signal.
>>> See the paper:
>>> http://www.timeok.it/files/5_and_10mhz_low_pass_notch_filter.pdf
>>>
>>> Luciano Timeok
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