[time-nuts] Reciprocal Counters

gsteinba52 at aol.com gsteinba52 at aol.com
Thu Jun 10 15:12:48 UTC 2010

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.

Message: 2 
Date: Thu, 10 Jun 2010 06:55:15 -0700 
From: jimlux <jimlux at earthlink.net> 
Subject: Re: [time-nuts] TPLL secret reveled 
To: Discussion of precise time and frequency measurement 
    <time-nuts at febo.com> 
Message-ID: <4C10EEC3.2030004 at 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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