Hi Mikael,
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I have a lot of experience using Si5351 on a breadboard using Adafruit and Amazon versions.? I even though the frequency of the crystal and transmit frequency is set correctly the signal is typically out of band.? This is due to the inaccuracy of the crystal.? The width of the band is only 200 Hz.? In the past I have had to fudge the transmit frequency to bring it into the band.? Typically the SI 5351 has two 3 inch pieces of wire for an antenna.? I use a standard ham setup for 20 m to receive it e.g. transmitter and tuned up antenna.
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When I power using the usb from a desktop computer, I get a lot of spike side bands that are easy to see.
?
Ken
K9YO
