Just an FYI guys, I'm pretty sure the 3rd circuit down on the Wenzel page is identical to the input circuit for the TAPR TADD-2 frequency divider. The TADD-2 adds a transformer and load resistor. Schematic is in the manual here:
http://www.tapr.org/~n8ur/TADD-2_Manual.pdf -Bob On Wed, Dec 8, 2010 at 8:46 AM, John Ackermann N8UR <[email protected]> wrote: > Wenzel has some discussion and circuits at: > http://www.wenzel.com/documents/waveform.html. > > The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL > chip for squaring. > > John > ---- > > > On 12/8/2010 10:31 AM, jimlux wrote: > >> I'm looking for suggestions on a general circuit that can be used to >> receive an external frequency reference (nominally a real clean sine >> wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it >> into a "real clean" square wave. Galvanic isolation is a plus (a >> transformer or capacitor would probably do that). >> >> I was thinking about rummaging through the schematics for test equipment >> reference inputs (since they've already "solved" the problem, eh?), but >> any other ideas would be welcome. >> >> I've scanned the archives of time-nuts, and while we have a fair amount >> of discussion on how to square up the 1Hz (or 100Hz) in a phase >> noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has >> commented that you don't want to use a comparator. I have the papers by >> Dick, et al, and Collins, as well as all the others.. they tend to be >> looking at the low frequency problem, although the analysis is certainly >> applicable. >> >> I don't know that I'm looking for the whole multiple limiting stages >> scheme in any case. >> >> Oh, as far as performance.. Say the need is to not horribly degrade a >> good quality crystal oscillator... here's a typical set of specs: >> 76 MHz >> 1Hz <-90dBc >> 10Hz <-110dBc >> 100Hz <-120dBc >> 1k-100k <-125dBc >> >> Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 >> sec, and back up to 2 E-12 at 1000sec. >> >> _______________________________________________ >> 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.
