[time-nuts] OT: xtal osc PN

[francesco messineo]

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.

Thanks again

Frank  IZ8DWF