[time-nuts] Why these Crystal Frequencies?

Rick Karlquist richard at karlquist.com
Thu Dec 15 12:45:49 EST 2011


16.384 MHz is of course 2^14 times 1 kHz.  This was used
as a clock for direct digital synthesizers in signal generators.
Most DDS's can't generate exact frequencies starting from a 10 MHz
clock.  There was  an Agilent arbitrary waveform generator that used this
as a clock because circular memory has a binary length.

The color burst frequency contains factors of 3,5,7,9, and 11, which are
important in terms of how early TV station hardware worked, using
multivibrator type frequency dividers.  11 is about the limit for those.

Rick N6RK

Brooke Clarke 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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