[time-nuts] 10 MHz -> 16 MHz clock multiplier

[Bob Bownes]

Paul Wade built a board recently to do just this. www.w1ghz.org.

Bob


On Fri, Jan 4, 2013 at 12:16 PM, Chris Albertson
<albertson.chris at gmail.com>wrote:

> THis is exactly what they are talking about the 74HC390 can do over
> 50MHz and costs abut 30 cents.  You don't need ECL or anything so
> exotic the 30 cent part will work.   Set it for divide by 5.  I guess
> this is imperfect enough that there is some fourth harmonic content in
> the 2MHz square wave, then you select that with a narrow band filter
> and amplify it to whatever you need.   A smart design might try and
> add fourth harmonics be using a slightly not-symetric 2MHz square wave
>
> 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.
>
> On Thu, Jan 3, 2013 at 6:02 PM, Tom Miller <tmiller at skylinenet.net> wrote:
> > Isn't there a fast divide by N counter that you could set to 10? Maybe
> even
> > in ECL?
> >
> >
> > ----- Original Message ----- From: "David" <davidwhess at gmail.com>
> > To: "Discussion of precise time and frequency measurement"
> > <time-nuts at febo.com>
> > Sent: Thursday, January 03, 2013 8:49 PM
> > Subject: Re: [time-nuts] 10 MHz -> 16 MHz clock multiplier
> >
> >
> >
> > They do not exist as I found out (again) not long ago.  The last 7490
> > made was LS (low power schottky) and I use quite a few of them.
> > Actually, I have seen a datasheet for a 74HC90 and 74HCT90 but they
> > apparently either never went into production or very few were
> > produced.
> >
> > The closest non-TTL alternative that I found was the 74HC390 or
> > 74HCT390 which is basically two 7490 counters in one package.
> >
> > On Fri, 04 Jan 2013 11:59:01 +1100, Max <vk3yba at gmail.com> wrote:
> >
> >> Where can one get some of these mythical  74HC90 's and 74AC90 's that
> >> have been mentioned.
> >>  None of the usual places have them, ie ebay, digi-key, farnell, or
> >> even the Chinese.
> >>  Also data-sheets are not to be found.
> >> Thanks
> >>
> >>
> >>
> >> On 4/01/2013 5:13 AM, Bill Fuqua wrote:
> >>>
> >>>     One way is to divide by  10 and then multiply by 16.
> >>> Divide by 10 and then follow by 4 tuned frequency doublers.
> >>> This should introduce little phase noise.
> >>>     Another way to do it is to divide by 10, then pass the output thru
> a
> >>> narrow 16 MHz filter and amplify. Sounds difficult but the filter can
> >>> be one
> >>> or two 16 MHz crystals followed by a simple amplifier. Look at the
> >>> reference input circuit for a PTS-160.  The output of the divide by 10
> >>> needs to
> >>> be asymmetrical so it produces even harmonics. If you are using a
> >>> divide divide by 5&2 such as a 74HC90, divide by 2 first then by 5.
> >>>  Ideally the pulse width should be a half period of 16 MHz for the
> >>> maximum harmonic content at 16 MHz.
> >>>     You can take the output of the frequency divider and send it to a
> >>> NAND gate.
> >>> One input of the gate is directly connected and the other is delayed.
> >>> You can
> >>> use an RC with a variable capacitor to ground to get it just right.
> >>>     Just adjust the capacitor to get the maximum output from your
> >>> filter amplifier.
> >>> 73
> >>> Bill wa4lav
> >>>
> >>>
> >>>
> >>> At 07:41 PM 1/2/2013 +0000, you wrote:
> >>>>
> >>>> What's the simplest way to generate 16 MHz from 10 MHz? This will be
> >>>> for clocking a microcontroller at 16 MHz given 10 MHz (Cs/Rb/GPSDO).
> >>>> Low price and low parts count is a goal; jitter is not a concern but
> >>>> absolute long-term phase coherence is a must.
> >>>>
> >>>> The ICS525 (as in TAPR Clock-Block) is a good candidate but I was
> >>>> wondering if there's something cheaper, less functional, and maybe
> >>>> not SSOP. Any suggestions?
> >>>>
> >>>> Thanks,
> >>>> /tvb
> >>>
> >>>
> >>>
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> >>
> >>
> >>
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>
> --
>
> Chris Albertson
> Redondo Beach, California
>
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