[time-nuts] ADEV

[Mike Feher]

I sure do agree, that with very low data rate systems it is significant. In
fact, when David Allan & Fred Walls came up with the proposal of using this
measurement as an FOM for oscillators over 30 years ago, digital
communication rates were slow, and, the measurement was a good one. Due to
the filtering process within ADEV by collecting and integrating a large
number of samples, has a filtering effect of its own. Therefore, it can, and
will, miss the fact that there may be instantaneous phase transitions that
could cause havoc with high data rates and higher order PSK modulation
schemes. So, again, I apologize, as I should have mentioned higher data
rates. However, you must admit that your application, while extremely
critical, is in the minority. I like to use the example of something like
DirecTV. Here, they use a down-converter that utilizes a free running DRO,
that is ridiculously noisy, and, varies all over in frequency, especially
over the temperature ranges it subjected to. In spite of all of that, one
gets a perfect pictures. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-901-9193 cell


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of jimlux
Sent: Friday, November 12, 2010 11:33 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] OT loosing things

Mike Feher wrote:
> Relax - we all need a little humbleness and humor every once in a while.
> Besides, I am honestly beginning to doubt the usefulness of ADEV in
today's
> communications systems, and yet it seems we are stuck on it. Regards -
Mike
> 
> 

You just need to look at a different kind of communication system.  If 
you're working at 8 bps like I do, or you want to measure the distance 
to a spacecraft around Saturn with an accuracy of millimeters, ADEV is 
important.

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