I think the thread branched and as I recall started something like this. Someone needed a "Simple" 16 Mhz for a uproc made from a 10 Mhz source. Two reasonable answers were given. Injection locked oscillator Typical div and mult/filter. A third and kind of interesting for me a Ti chip soic digital pll. Then the thread went a whole bunch of directions. Wonder if who ever needed an answer got the answer? Regards Paul WB8TSL
On Fri, Jan 4, 2013 at 7:18 PM, <ewkeh...@aol.com> wrote: > How about getting back to basics. > Is it a one off, if production how many and what are the specification > requirements? Otherwise on this list it can go on for a year. > Bert Kehren > > > In a message dated 1/4/2013 6:11:14 P.M. Eastern Standard Time, > wlfuq...@uky.edu writes: > > At 07:51 PM 1/4/2013 +0000, you wrote: > >My question is about the phase noise of the final 16MHz signal. Do > > > crystal filters "clean up" the signal. It seems that after several > > > 16MHz crystals in series the output should look a lot like an XO. > > > > > > >For offsets out to 100 Hz or so, using a crystal filter will cause > >the signal to have the same flicker noise that an oscillator built > >with that crystal would have. Thus don't try to use some junky > >clock crystals to make a crystal filter as described in numerous > >ham radio articles about receiver IF filters. If you have a > >residual phase noise measurement system like the Agilent E5505A > >and a very low flicker noise source, you can actually measure your > >filter crystals. Of course, the crystal time base in the source > >has to be better than the crystals you are measuring. You also > >have to avoid overdriving the crystal. This will require a low > >noise buffer amplifier to bring the signal back up to a high > >level. > > > >Now after considering all that, crystal clean up filters don't > >sound like such a great idea unless you have no alternative. > > > >Rick Karlquist N6RK > Flicker noise (1/f ) noise would be introduced by an amplifier and not > by the filter. I am only suggesting ways to multiply the frequency. > You could use LC filters or a crystal filter. Using 3 doublers would > do the job just as well. Naturally if you are concerned about flicker > noise > you could simply make the 2 MHz signal higher in amplitude before > selecting > the 8th harmonic. > I was not saying your going to clean up a good crystal oscillator with a > crystal filter. I though you were talking about generating 16MHz from > 10MHz > in a clean way. Using a microcontroller or even most synthesizers > techniques would make > it even worse. > The PTS synthesizers have fairly good phase noise when they use > frequency multiplication, > division, mixing, comb generation and filtering on the most part to > achieve > low phase noise. > The later models use a DDS at the lower frequency levels but do have > greater phase noise > close to the carrier. In fact in the SGA unit the reference input goes > thru a transistor ( to distort it) > and then into a series 10MHz crystal filter so that it can accept either a > 5 or 10 MHz input. > The crystal also helps filter out any birdies that may be on the > reference signal. > The filter should be fairly high Q since it has 47 Ohm drive impedance and > 100 Ohm load impedance. > 73 > Bill wa4lav > > > > _______________________________________________ > 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. > _______________________________________________ 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.