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 <[email protected]>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 <[email protected]> wrote: > > Isn't there a fast divide by N counter that you could set to 10? Maybe > even > > in ECL? > > > > > > ----- Original Message ----- From: "David" <[email protected]> > > To: "Discussion of precise time and frequency measurement" > > <[email protected]> > > 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 <[email protected]> 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 > >>> > >>> > >>> > >>> _______________________________________________ > >>> 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. > > > > > > _______________________________________________ > > 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. > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > 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.
