Well that makes sense.
A 50 ohm load is asking an awful lot from the CMOS output of the si5351.
The si5351 has only one pin for the 3.3v rail.
Loading multiple outputs heavily means the internal 3.3v rail will be getting jerked around,
and you will see crosstalk between those outputs.
You might try adding a buffer amp between the si5351 and your 50 ohm load.
Perhaps steal the buffer at Q7 from the bitx40 at ???Q7 is an mmbt3904.
Jerry
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On Wed, Oct 25, 2017 at 04:32 am, Jean-Matthieu F5RCT wrote:
I'm sorry but the spurs are getting worse if I terminate all outputs to 50 Ohms !
If only one ouptut is activated the signal is clean !
