[time-nuts] wwvb 60 khz tuning fork crystals Some insights

[Don Latham]

Maybe the old 4007 cmos would be better...
Don

paul swed
> 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
> <n1hac at alum.dartmouth.org>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 <eb at telight.com> 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
>>>>
>>>>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
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