On Mon, Nov 28, 2011 at 7:14 PM, Michael Malloy <[email protected]> wrote: > yeah it is squaring up, but not great I have already designed the > circuit boards, hmm > maybe if i replace the 74HC04 with a 74HC14 (schmitt trigger input) > which I do not have > I did make a surface mount single gate schmitt trig after the 74HC04 > as I knew that > this squares things up much better, however after the 74HC04 it goes to > a 74HC4040 divide by 12 counter and from that input it goes to another > 74HC04 into the processor > I am worried that the fact that the counter and the processor are 90 > degrees out of phase clock cycle > if I put the single gate schmitt trig in it will bring both in phase > I may need to make software adjustments if this happens?? > > and no I did not test the unit without any load, I had a hombrew TCXO > in the original > circuit but its performance was only +- 10PPM and caused problems with the > codec > its a very sensitive design to jitter, TXCO was cheapest option but if > I had the money would have put an OCXO > in but they are not cheap in small runs, I am getting off track > I will take a picture of my oscilloscope and post it > > let me see if the 74HC14 is pin for pin compatible with 74HC04 maybe I > will replace with this. > but I do not think I have any here > > On Mon, Nov 28, 2011 at 6:36 PM, Attila Kinali <[email protected]> wrote: >> On Mon, 28 Nov 2011 16:15:37 +1100 >> Michael Malloy <[email protected]> wrote: >> >>> Hi all I ordered a 8.192MHZ TCXO 1.0PPM >>> Now it was supposed to have a clipped sine wave output? however it >>> looks more like a saw tooth, I assumed a clipped sine would be a sine >>> wave with the peaks clipped, I am running this through >>> a 150pF cap and then using a inverter amplifier i.e. 74HC04 with a 1M >>> resistor from input to output. >>> >>> am I over loading or loading down the the oscillator, or should I be >>> changing the buffer capacitor? >>> I mean the circuit is working but its not 45/55 duty cycle >>> the out put looks like the first 0 -90 degrees of a sine wave then >>> drops to zero stays there for about 20% of the duty cycle then ramps >>> back up? >> >> Do you measure the TCXO raw, w/o any circuitry attached? >> Because this sounds rather like that the 74ZHC04 is messing >> with the signal. Maybe the 1M resistor isnt really 1M? >> >> Other than that, i would feed the output directly to >> a 74HC14 (schmitt trigger input) to square it. If you >> want to have precise or adjustable duty cycle, you can also >> use a comparator (but make sure to include enough hysteresis, >> otherwise the comparator might oscillate) >> >> >> Attila Kinali >> >> -- >> Why does it take years to find the answers to >> the questions one should have asked long ago? >> >> _______________________________________________ >> 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. >> > > > > -- > #include <sig.h> > /* ================ */ > Michael > /*How crazy does it get on the moon, when theres a full Earth?*/ >
-- #include <sig.h> /* ================ */ Michael /*How crazy does it get on the moon, when theres a full Earth?*/ _______________________________________________ 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.
