Hi As I recall the spec was:
1) Cheap 2) no phase slips on the 16 MHz relative to 10 MHz 3) Cheap Bob On 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.