Hi Piotr, many thanks for the link, I didn't know that page! Best regards
Frank IZ8DWF On Mon, Sep 20, 2010 at 12:05 PM, Piotr Kolodziejczyk <[email protected]> wrote: > Hi Frank, > > SM5BSZ has interesting article about measuring low PN oscillators. > > http://www.sm5bsz.com/osc/osc-design.htm > > He also describes there his NEWREF which achieved -179.5 dBc/Hz. > You could use it as practical design example. > > Regards, > Piotr, sp3ukk > > > On Sun, Sep 19, 2010 at 10:40 PM, Mike Feher <[email protected]> wrote: > >> Frank - >> >> DBMs are extremely cheap in the frequency range you are talking about. The >> rest, well, you just have to try. I think you are way overcomplicating >> this. >> I am still not sure why you feel you need a xtal filter. It is not going to >> help with the 100 Hz away stuff. Using simple BJTs common base >> configuration >> would give you more than enough isolation for what you are doing. Besides, >> I >> believe you will only be using one output at any given time. Sounds like >> you >> need to experiment and learn. Else just do it and see what you get. That is >> what all of us did when we needed something special, and then that way >> learned what to do and what not. As I said, nothing about your approach >> seems magical or even difficult. I have been a ham for almost 50 years. >> While in HS everything I built worked just fine. The more education I >> received the greater my expectations became, however, it did not need to >> over complicate matters. 73 - Mike >> >> Mike B. Feher, N4FS >> 89 Arnold Blvd. >> Howell, NJ, 07731 >> 732-886-5960 >> >> >> >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of francesco messineo >> Sent: Sunday, September 19, 2010 4:12 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] OT: xtal osc PN >> >> Hi Mike, >> >> On 9/19/10, Mike Feher <[email protected]> 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 >> Frank >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
