really slow PLL

John Larkin · 2022-07-20T23:20:57+00:00

Suppose I have several rackmount boxes and each has a BNC connector onthe back. Each of them has an open-drain mosfet, a weak pullup, and alowpass filtered schmitt gate back into our FPGA. I can daisy-chain several boxes with BNC cables and tees.Each box has a 40 MHz VCXO and I want to phase-lock them, or at leasttime-align them to always be the same within a few microseconds,longterm.I could call one the leader (not "master") and make the othersfollowers (not "slaves") and have the leader make an active low pulsemaybe once a second. A follower would use her (not "his") clock tomeasure the incoming period and tweak its local VCXO in the rightdirection. That should work.Don't GPS receivers lock their 10 MHz oscillators to a 1 PPS pulsefrom the satellites?My system should work from a 1 PPS GPS pulse too, all boxes asfollowers.The PLL algorithm might be interesting.

Jul 20, 2022 Last reply: 3 years ago 169 Replies

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Les Cargill 3 years ago

Just so. I think of solo concert pianists as the people who woodshed the most. But they can probably produce a passable rendition on first read.

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Martin Brown 3 years ago

It works well and was very cost effective. Tapes got reused after a while..

The recent black hole images were using about 5e15 bytes of data each.

Disks and mass storage capacity generally have got a lot bigger. The plastic chips in Star Trek (original) look huge in comparison to sD.

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