Just a speculation on my part, but if you got some non-saturating logic like
ECL, the jitter would be less.
I haven't done any ECL in years, but the traces I got from ECL circuits are
amazingly clean. I was evaluating a competitions ECL DAC.
-----Original Message-----
From: skywatcher <skywatc...@web.de>
Sender: time-nuts-boun...@febo.com
Date: Thu, 19 Apr 2012 21:10:03
To: <time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: [time-nuts] Question about precise frequency / phase measurement
Hello @all,
my name is Wolfgang and i'm new to the list. :)
I browsed through the list archive, but i didn't find the infos i need,
so i decided to join the list
and to ask the experts directly. :)
I want to measure the frequency difference between a 10 MHz OCXO and a
10 MHz Rubidium.
I think that's what many people here have done many times... but i don't
want to use expensive
equipment like time interval counters with picosecond resolution etc. I
would prefer a cheap and
easy solution. I also would like to have an update rate of more than 1
measurement per second,
or even more.
My first approach was to use a simple XOR phase comparator. I tried a
74HCT86 and a 74HCT4046.
It works, but it's very noisy, so i don't get better than about 10 mHz
frequency resolution.
If i look at the lowpass-filtered output i don't see a nice sine or
triangular wave, but it looks more
than a triangular wave with round tops and some bumps between them.
Another problem is that the
difference frequency gets very low when the frequencies are very close,
so it's not enough to look
only for zero crossings of the difference signal.
Does anybody know a possibility to get a resolution < 1 mHz ?
Best regards,
Wolfgang
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