[time-nuts] Holdover, RTC for Pi as NTP GPS source

Leo Bodnar leo at leobodnar.com
Thu Nov 2 17:45:56 EDT 2017

This is, essentially, how modern delta-sigma DACs work while achieving 24-bit and higher precision using only a single bit converter internally and a lot of clever digital filtering.
Multiple loops are what would be called "higher order" in delta-sigma parlance.
Delta-sigma tech is not poor man's DAC - it has properties that other conversion methods can't achieve, e.g. noise shaping and trivial aliases rejection.
I suspect delta-sigma body of knowledge can be applied almost wholesale to this seemingly silly oscillator concept. 
Did I just repeat something trivial that has been discussed to death here before? 

> From: Bob kb8tq <kb8tq at n1k.org>
> Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source
> There’s no particular reason to stop at the 100:1 point. You can run multiple 
> loops at the same time and get out to essentially any level of precision. The
> only question is over what averaging interval the precision applies.

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