Yes it makes a very fine 35 Mhz oscillator and reasonably stable. Been there and done that. Hey the systems done. May remod it one day but bigger fish to fry with the d-psk-r Regards Paul WB8TSL
On Thu, Jun 27, 2013 at 6:41 PM, David McGaw <[email protected]>wrote: > Lower gain is better as long as it oscillates. The 74HCU04 is unlikely to > drive spurious responses. The 74HC04 is OK as long as you keep the > feedback gain low - sometimes a series resistor from the output to the > resonant circuit is required. A 74HC14 is the WRONG part for the job as it > can and will oscillate without the crystal controlling it - just try it > with a resistor for feedback and a capacitor to ground at the input, no > crystal. > > David N1HAC > > > > On 6/27/13 6:30 PM, paul swed wrote: > >> I will say the fact is the 74hc14 is a bit of a power pig we are talking >> 12 >> ma. The rcvr is something much less like 100 ua. At least for the moment >> it >> all works but 12 ma is a pig. >> Especially when you take the signal out and knock it down to 100-200 uv. >> Regards >> Paul. >> >> >> On Thu, Jun 27, 2013 at 5:37 PM, ed breya <[email protected]> wrote: >> >> Still having email problems - here we go again. This is second try, >>> please >>> excuse if both show up. >>> >>> >>> Hal Murray said: >>> >>>> They make 74xU04 for many values of x. The U is for Unbuffered. They >>>> >>> have >>> lower gain in the linear region. >>> I thought they were intended to be used for things like this, but I don't >>> understand that area. Can anybody give me a quick lesson or point me at >>> a >>> good URL?< >>> >>> >>> >>> I always thought the unbuffered "U" versions were preferred for ring >>> oscillators mostly to save power - you don't want the high-drive output >>> stages to be cooking away in linear mode if not needed. The propagation >>> delay can also be less since the U ones have only one stage instead of >>> three (the building block is the totem-pole inverter stage), but they >>> can't >>> drive very much load anyway. I think that most MSI and LSI parts that >>> have >>> built-in ring/crystal oscillator sections use the U topology, but I don't >>> think there's anything special about it - it's the simplest thing that >>> works. >>> >>> I've made quite a few CD4000 and 74HC oscillators, and never worried too >>> much about U versions or not, except for battery-run items where power is >>> critical (or you can run the oscillator at lower voltage). Often they are >>> made from inverting gates that are part of a shared package, where you >>> wouldn't want puny drive capability in the other gates anyway. They are >>> relative power hogs though, whenever linear biasing is needed. Except in >>> the 4000 series, I don't know if U versions are available in anything but >>> the '04 hex inverter, but I suppose it's possible. I think the >>> Schmitt-trigger types like HC14 are necessarily buffered, so have three >>> stages, since you need a non-inverted version of the signal for the >>> positive feedback to the input. >>> >>> I've never tried making one in 74AC - I don't know if it's even possible >>> to bias one up that way without it burning up. I'm working on some >>> related >>> circuits now, so maybe I'll set up an experiment to see how much current >>> it >>> would take for one inverter - I've often wondered about this. >>> >>> I read about this years ago in various CMOS application notes, so I may >>> be >>> missing some key points - there should be plenty of info online. The >>> older >>> generation (when CMOS was fairly new) info may provide more detail about >>> the guts than that related to the newer, higher performance families. >>> >>> Ed >>> >>> >>> ______________________________****_________________ >>> >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/****<https://www.febo.com/cgi-bin/**> >>> mailman/listinfo/time-nuts<htt**ps://www.febo.com/cgi-bin/** >>> mailman/listinfo/time-nuts<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<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<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.
