[time-nuts] what is the best way to multiply a 10 Mhz signal?

Christophe Huygens Christophe.Huygens at cs.kuleuven.ac.be
Tue Dec 21 13:37:11 EST 2010

You may want to check out the 10MHz locked 1GHz clock I did
(using ADF4107 and a 1GHz Crystek CVCO)
and associated DDS to generate oddbal frequencies.

Includes some PN measurements.


On 21/12/10 19:18, Mike Feher wrote:
> Interesting. When I used to use and build DDSs back in the early 70's, we
> typically used 2.56 times the maximum required frequency for a clock, to get
> above Nyquist and allow adequate filtering stop-band rejection. At the time
> we could not go much higher due to limitations in device speeds, especially
> the D/A. Today you can easily use a much higher clock frequency which would
> simplify filtering and reduce gain variations. At 70 MHz clock you are only
> at 2.333 Nyquist. Even at 2.56 by the time you get to your desired goal of
> 30 MHz, you will have what looks just about like a square wave. So,
> filtering will be a must, and, after filtering, you will find that your
> amplitude output will greatly decrease with frequency. The other question is
> phase noise objectives. If that is not a real concern, then as suggested,
> maybe a simple locked VCO would be the way to go. 73 - Mike
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Stephen Farthing
> Sent: Tuesday, December 21, 2010 12:57 PM
> To: Richard (Rick) Karlquist; time-nuts at febo.com
> Subject: Re: [time-nuts] what is the best way to multiply a 10 Mhz signal?
> Hi Rich....
> Thanks for the reply....I have an AD9834 DDS chip I want to use for a
> Frequency generator with an accuracy of 1 Hz from 0-30 Mhz. . This part can
> be clocked at 75 Mhz - but unlike other DDS chips seems to have no internal
> clock multipliers. So it seems to me if I can some how generate a 70 Mhz
> clock signal from my rubidium standard I can solve the problem.
> 73s Steve
> On 21 December 2010 17:36, Richard (Rick) Karlquist
> <richard at karlquist.com>wrote:
>> I used to be in the synthesizer business (Zeta Labs)
>> in a previous life.  I learned to ask the customers:
>> what you are trying to accomplish as the end goal,
>> before tackling a messy problem like multiplying by
>> 7.  Maybe you don't need to multiply by 7, but we
>> can't tell from your question.
>> Rick Karlquist N6RK
>> On 12/21/2010 8:35 AM, Stephen Farthing wrote:
>>> Hi everyone,
>>> I want to multiply the output from my Efratom 101 (10Mhz) to clock a DDS
>>> at
>>> 70 Mhz. Has anyone tried this?
>>> Regards,
>>> Steve G0XAR

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