On Fri, Jan 17, 2020 at 09:44 AM, Jerry Gaffke wrote:
Herb,
Actually, two different odd harmonics get used.
From Erik's post of
/g/nanovna-users/message/1743You are explaining well, except the SW uses above 300MHz the 3rd harmonic of one clock and the 5th harmonic
of the other clock to avoid detecting the 3rd harmonic of the mixing product of the 1st harmonics of the clock's
Example 200MHz + 200.00166MHz produce from 1st harmonic 1.66kHz which will include a certain amount of 3rd harmonic at 5kHz.
Using 200MHz + 120.001MHz produces only 5kHz when their 3rd and 5th harmonic combine
Also, the Si5351 is spec'd to operate at up to 225 mhz, anything beyond that is a gift.
Those for which the PLL craps out at 290 mhz are not necessarily from "shady sources".
Perhaps just cut from the outside edge of the wafer, but still perfectly compliant with the spec.
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Jerry,
Thanks for adding the additional information. I oversimplified in trying to stay in line with the "over-clocking analogy". I can always depend on other user's like yourself to add to the discussion with more in-depth info. That's what makes this forum a cut above.
- Herb
