[time-nuts] 10MHz to 25MHz

Bob Camp kb8tq at n1k.org
Thu Jan 19 16:18:24 EST 2017


Hi

> On Jan 19, 2017, at 2:42 PM, Bryan _ <bpl521 at outlook.com> wrote:
> 
> Wouldn't designing circuitry and PCB's be easier with 10Mhz vs 100Mhz? Maybe not so much now but then.

Design in general might be a bit easier at the lower frequency “way back when”. I’ve never run into 
it as an issue or consideration since the mid 1960’s though. 

Bob

> 
> 
> -=Bryan=-
> 
> 
> ________________________________
> From: time-nuts <time-nuts-bounces at febo.com> on behalf of Charles Steinmetz <csteinmetz at yandex.com>
> Sent: January 19, 2017 4:13 AM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] 10MHz to 25MHz
> 
> Chris wrote:
> 
>> I have always wondered why we build our "standard" with such a low
>> frequency.   Why not a 100MHz GPSDO?   Why 10MHz
> 
> Quartz crystals work better at lower frequencies, predominantly because
> they have higher Q.  10MHz was chosen because it is low enough for
> excellent performance but high enough to be directly useful (since an
> accident of biology gave us ten fingers, we've created a base-10 world
> and powers of 10 are favored in almost everything).
> 
> In prior times, 5MHz crystals held this position, and before that, 1MHz.
>  There is a good argument even today that the best 2.5MHz or 5MHz
> crystals are better than the best 10MHz crystals, but not by enough to
> make 2.5MHz or 5MHz standards popular any longer.
> 
> One lonely data point, which proves nothing:  My best crystal oscillator
> is a Symmetricom clone of the double-oven HP 10811s (it came out of an
> HP GPSDO, so apparently HP at one time used them interchangeably with
> the 10811).  That OCXO uses a 5MHz crystal and a frequency doubler to
> produce its 10MHz output.
> 
> Best Regards,
> 
> Charles
> 
> 
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