[time-nuts] Generating 66.666...MHz from 10MHz

Murray Greenman Murray.Greenman at rakon.com
Sun Jun 28 19:07:33 EDT 2009

Here's an idea which actually works (I tried it). Rather than lock at
10MHz, you lock directly to 1pps.

You can lock an XO to 1/3 Hz steps by locking to 1pps and ignoring two
out of three results from the TIC. I did it at 7.333MHz, using an
AT90S2313 micro, and you could just as easily do it at 8.333... and then
multiply by 8.

Yes, it does leave you with a very low loop frequency! Although I've not
tried it, you could potentially add 120 degrees equivalent to one
intermediate TIC result and subtract 120 degrees from the next, and so
lock at 1Hz.

Murray ZL1BPU

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