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 <[email protected]> Subject: Re: [time-nuts] TPLL secret reveled To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> 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. ------------------------------ _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
