Hi Jim,
You're showing your age (you young whippersnapper!).
?? "They've been around at least since the 80s,..."
Well, my General Radio 1159 Recipromatic Counters are from 1968 - built using
those new transistor thingies and with the warm glow of Nixie tube readout.
Best,
Jerry
Message: 2
Date: Thu, 10 Jun 2010 06:55:15 -0700
From: jimlux <jim...@earthlink.net>
Subject: Re: [time-nuts] TPLL secret reveled
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Message-ID: <4c10eec3.2030...@earthlink.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Ulrich Bangert wrote:
>
>
>
> The next improvement to the old fashioned pure counter was the invention
of
> subclock interpolation schemes. A counter using this works so: After the
> beginning of the gate time it waits of the next zero crossing and then
> measures the time up to the last zero crossing within the gate time with a
> fixed resolution of say 1 ns (like the well known Racal Dana
> 1992/1996/1998). The frequency value is then the result of a computation.
If
> you consider this working principle you notice that this is even more a
> phase meter like thing than the original counter only thing. For that
reason
> frequency measurements with a counter like that are suited as well for
ADEV
> calculation.
>
I've always referred to these style counters as "reciprocal" counters..
(because the frequency is calculated as the reciprocal of the length of
N periods of the input signal). They've been around at least since the
80s, especially for applications where you need short gate time, but
measurement precision greater than 1/gate time. It was very popular for
applications like intercept receivers in the signals intelligence area
before straight digital processing (ADC and FFT) was practical.
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