[time-nuts] OT: xtal osc PN

Magnus Danielson magnus at rubidium.dyndns.org
Sat Sep 18 13:08:01 UTC 2010

On 09/18/2010 02:41 PM, francesco messineo wrote:
> First of all, thanks to John and Magnus for inputs and links, makes a
> very good start!
> On 9/18/10, Magnus Danielson<magnus at rubidium.dyndns.org>  wrote:
>> On 09/18/2010 09:48 AM, francesco messineo wrote:
>>> Hello all,
>>> sorry for the OT, but the electronic expertise of the group is too good
>>> :-)
>>> I'm looking for ideas and directions (articles and so on) to realize
>>> very good phase noise xtal oscillator, in the range 20-50 MHz for high
>>> performance frequency conversion. I would like to understand what
>>> circuits can be realized (not requiring too much professional and
>>> modern equipment, test eq. from the 70s-80s is ok) and what is the
>>> contribution of the active oscillator device, the xtal itself and the
>>> following buffers.
>>> Another idea that came on my mind was using digital oscillator (square
>>> wave, cmos) and then filtering for sine output, if this makes sense
>>> for a low PN point of view.
>>> Is there any way to measure the close-in PN of oscillators with an
>>> amateur setup?
>> First of all I think you need to quantify what you mean by "high
>> performance frequency conversion" and what stability measures you are
>> seeking as there are many degrees of excessiveness to attempt, and many
>> of them may be well beyond what you need. Remember, we are time-nuts... :)
> Ok, let's say as good as practically and economically feasible for
> "single" prototype and homebuilder. I already chosed not to use a
> Si570 because I really need only few (2-4) fixed frequencies and I'm
> assuming that carefully made xtal oscillators can beat the Si570 phase
> noise performance.
> The conversion is obviously for a receiver, not for  the classic HF
> bands, but  for the lower VHF amateur bands (50-70 MHz) where IMD3
> performance of the receiver has to be the best possible, as these
> bands are used for TV and radio broadcasts in many nearby countries
> around here.
> Of course a very good frontend BPF, amplifier and mixer are needed,
> but these are less of a problem for me to chose (and are simpler to
> evaluate with "standard" test equipment too).
> Unfortunately I know very few  low-VHF-nuts and very few of them (if
> any) realize their setup performance are so far distant from what can
> be achieved nowadays.

I just recalled, you do want to check out John Miles (KE5FX) GPIB 
toolkit, the PN.EXE software will let you use your spectrum analyzer (if 
supported) to measure phase-noise. For your purpose it should be useful 
for you. For some of my phase-noise needs my tools isn't sufficient yeat 
to do some of the phase-noise measurements I want.

John's home:

John's GPIB toolkit:

John's TimeLab:

I was able to contribute support for my spectrum analyzer with some good 
help from John. Happy to see it being part of the distribution now.


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