[time-nuts] Why these Crystal Frequencies?

Eric Garner garnere at gmail.com
Thu Dec 15 14:14:46 EST 2011


Brooke,

25 MHz (and to a lesser extent 50 MHz) is used to clock Ethernet PHYs.
It's multiplied up to the various clocks needed internally
(125,250,625 MHz etc.)

-Eric

On Wed, Dec 14, 2011 at 7:13 PM, Brooke Clarke <brooke at pacific.net> wrote:
> Hi Pete:
>
> Maybe you can shed some light on the common xtal frequencies table where
> there's no explanation given?
> http://www.prc68.com/I/pdf/Crystal_Freq.pdf
> An answer is not it's an "even" frequency or "it's an even binary frequency.
> That's true for most of these and the factors are part of the table above.
> The question is why do they exist?
> such as:
> 32.0 kHz
> 40.0
> 75.0
> 76.79
> 76.8
> 76.81
> 96.0
> 3.072 MHz
> 4.0
> 4.096
> 5.0
> 6.0
> 7.3729
> 8.0
> 8.192
> 9.8304
> 10.0
> 11.0
> 11.0592
> 11.2896
> 12.0
> 12.288
> 12.352
> 13.5
> 14.31818
> 15.36
> 16.0
> 16.384
> 17.734475
> 18.0
> 18.432
> 19.6608
> 19.44
> 22.1184
> 24.0
> 24.567
> 25.0
> 25.175
> 28.63636
> 30.0
> 1.4204058 GHz
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/Brooke4Congress.html
>
>
> Peter Bell wrote:
>>
>> It's exactly 52 times the 1.2288MHz reference that IS95/CDMA2K uses -
>> this may be a coincidence, but I somehow doubt it.
>>
>> Regards,
>>
>> Pete
>>
>>
>> On Thu, Dec 15, 2011 at 3:46 AM, Joe Leikhim<JLeikhim at leikhim.com>  wrote:
>>>
>>> I have been watching this thread and may have missed something. My
>>> questions: What is the purpose of the outboard OCXO VECTRON 63.8976Mhz?
>>> What
>>> model number does this RB most closely resemble?
>>>
>>> --
>>> Joe Leikhim
>>>
>>> Leikhim and Associates
>>> Communications Consultants
>>> Oviedo, Florida
>>>
>>> www.Leikhim.com
>>>
>>> JLeikhim at Leikhim.com
>>>
>>> 407-982-0446
>>>
>>> Note to GMail Account users. Due to an abnormally high volume of spam
>>> originating from bogus GMail accounts, I have found it necessary to block
>>> certain GMail traffic. Please phone me if you believe your message was
>>> not
>>> received.
>>>
>>>
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-- 
--Eric
_________________________________________
Eric Garner




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