[time-nuts] How to measure Allan Deviation?
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun Oct 22 21:53:07 EDT 2006
John Miles wrote:
> You can do a lot worse than straight TTL. Some useful graphs on pages 102
> and 103 of Rohde's "Microwave and Wireless Synthesizers: Theory and Design".
> Hint: Look it up at www.amazon.com and you can view those two pages, if you
> search within the book for the phrase "170 dB".
> -- john, KE5FX
>> The few experiments I've done indicate that there isn't that much
>> sample-to-sample jitter in a divider built up out of a reasonable-length
>> string of 74HC390 dividers, but the temperature stability is horrible.
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> time-nuts at febo.com
I have a copy of this.
However I find that these graphs appear somewhat inconsistent.
Figure 2-15 should be used for comparing the various logic families.
For a valid comparison the input frequencies and output frequencies
should be the same.
When you actually critically examine the data, TTL is nowhere near as
good as implied by the text.
This book is somewhat variable in the quality of its information.
Some of it is very good, some of it is just incorrect.
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