dave vanhorn wrote:

> Odd harmonics are the worst. Most digital stuff is square waves, and as
> Fourier showed us, they consist of all the odd harmonics. I take each
> crystal frequency, and scan each odd harmonic up to 1GHz with an Icom
> R-8500 receiver. The FCC tests you from 30-1000 MHz on radiated noise.
>
> To keep the oscillator quiet is really very simple.
> Use the right loading caps. This also means that your xtal will be "singing
> the right tune"
> Connect the caps at the crystal, and run a single track back to the uP
> ground pin.
> Don't dump it into a plane, and don't let anything else use this track.
> Make the crystal tracks paralell, as short as possible, and as close to
> each other as possible.
> I also route exclusively with curved traces, which limits the impedance
> discontinuities at corners. This is a real small effect, but curved tracks
> are free, so I just do it.

Thanks a lot vor your very comprehensive explanation in getting a
circuit quiet.

So when I use the right load caps for the xtal I4ll get the smallest
amplitdes at the odd harmonics ?

Kind regards

        Stefan