[time-nuts] 74HCT9046A Max. Operating Frequency

Tim Shoppa tshoppa at gmail.com
Tue Apr 29 06:46:00 EDT 2014


Interesting, I had never read AES11 before, I see they are not just scaling
to the facility but to drop hints of worldwide synchronization in there. I
would like to compare/contrast the evolution of digital timecode
distribution (AES11 spec for 1ppm), with where nationwide conventional TV
distribution was 40+ years ago (proposal for using for time-transfer with
sub-microsecond jitter and microsecond level drift over several months):
http://tf.nist.gov/general/pdf/237.pdf


On Mon, Apr 28, 2014 at 4:19 PM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> You actually have to look in AES11 and see that Grade 1 is specified to be
> within +/- 1 ppm with a minimum capture range of +/- 2 ppm while Grade 2 is
> +/- 10 ppm with a minimum capture range of +/- 50 ppm.
>
> AES5 does give you the +/- 10 ppm minimum requirement for the source, but
> nothing about the receiver.
>
> Cheers,
> Magnus
>
>
> On 04/28/2014 02:45 PM, Tim Shoppa wrote:
>
>> I suspect the TCXO might not have enough range because fundamentally the
>> VCTCXO are only 10ppm range and your AES3 source could well be much
>> further
>> off unless it is being run from a better master clock than a TCXO.
>> +/-50ppm
>> is the hope for pro-grade AES3 streams. I think AES5 is aiming towards
>> clock rates in the 10ppm ballpark.
>>
>>
>>
>> On Mon, Apr 28, 2014 at 2:41 AM, sg sg <micpreamp at yahoo.de> wrote:
>>
>>  Thanks very much for your responses!
>>>
>>>  For 24.576 MHz VCXO, the fractional change in frequency will be in
>>>>
>>> multiple
>>>
>>>> ppm not octaves, and I would naturally gravitate towards a simple diode
>>>>
>>> DBM.
>>>
>>> To avoid lock issues I'd still want a phase-frequency detector; the PLL
>>> bandwidth in my case is very low (a few Hz), which makes the lock range
>>> tiny if a "phase only" detector is used (I've run into this recently with
>>> some other project).
>>>
>>>  24,576 MHz is 128x192 kHz which makes essentially any divide by 2^N chip
>>>> capable of the frequency a target. Is your reference signal also 24,576
>>>> MHz or some other frequency?
>>>>
>>>
>>> The source is an AK4114 AES/EBU audio receiver, which has both master
>>> clock (24.576 MHz) and "word select" rate (48-192 kHz) outputs. Perhaps
>>> it
>>> is better to run the PLL at the latter? Any disadvantages from this?
>>>
>>> Regards,
>>> Samuel
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