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: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] 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 <mfe...@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 Frank _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.