The etherkit and si5351bx routines leave the pll/vco where it's at,
and only change the output multisynth fractional divider.
The effect is instantaneous.
And while I believe the waveform has no first order discontinuities,
the sudden change in frequency would give it sidebands that may be objectionable.
Especially at high power levels.
One of the DDS chips would give much more control, though not at the same price.
This is all just armchair conjecture.
Jerry, KE7ER
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On Mon, Oct 30, 2017 at 05:12 am, Hans Summers wrote:
Hi Farhan
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Great project! I am surprised that it works, though! I thought the PLL settling time of the Si5351A would be too slow to allow NBFM by applying FM to the reference crystal.?
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I once tried very quick frequency change commands issued by firmware to the Si5351A but it could not cleanly keep up with more than a few hundred Hz. Let me know though if you find differently!
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73 Hans G0UPL
