[time-nuts] OT: xtal osc PN

francesco messineo francesco.messineo at gmail.com
Sun Sep 19 20:11:57 UTC 2010

Hi Mike,

On 9/19/10, Mike Feher <mfeher at eozinc.com> wrote:
> Frank -
> Great idea, so obvious I did not think of it. If you mix the 20 and 22 you
> will only get 3 dB degradation or still very close to the -131 dBc/Hz
> relative to the 10811A. As I mentioned before the architecture is relevant.
> I have found that mixing does not cause any noticeable degradation, and I
> used to go all the way up to 45 GHz on military programs where it was very
> critical. At the frequencies you are talking about I doubt if the amplifiers
> will have any appreciable degradation either. Of course you have to keep
> levels in perspective, as you will not do better than kT. I also do not
> believe that dividers will have much impact. After all, a DDS is a
> divider/counter and accumulator, and PN is usually considered to be very
> close to  20logN better at the output than the reference, however, DDS does
> have spurious at most frequencies, but that is a discussion for another
> time. I still think your original thought is your best approach. Fast, easy
> and less than $100, even if you do use a used 10811A. 73 - Mike

this approach as I said has a lot of unkown to me, for example, how to
divide by 5 (ttl or cmos or maybe synchronous or something else?),
then there's the doubler (diodes? jfet?), then the mixers: need them
to be diode mixers (a classic double balanced? can be  homebrewed or
better use ready-made?) or I can get away with something cheaper like
fet mixer or something else?
Finally the xtal filters, those need to be ordered, where? what
exactly do I need as filter here in terms of poles or number of xtals?
Not to mention I need to "reuse" many of the signals, this means a few
isolation amplifiers with good isolation.
After posing myself these questions I thought I might evaluate other
approaches :-)

Best regards

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