Plug in the Si5351

Noise on WSPR waterfall display

I felt that running the Si5351 from the breadboard might be the cause of some noise I was seeing on the WSPR waterfall display.  Maybe the 10 cm jumper wires were radiating clock pulses.  And the breadboard connections were not reliable; signals would drop out and a little wire wiggling would cause them to pop back in.

Si5351 plugged into µBITX

I soldered 0.1uF caps and ground wires onto the Adafruit board (as described at ubitx.net) and pushed the ends into the µBITX connector.  The connection is much more secure now.
But the noise is still on the WSPR waterfall display.
My next theory is that the Teensy LC is radiating some digital noise.  I applied the Snooze library to put the µC to sleep and see if that makes a difference.  So far, I still see the noise.

Noise or not, I am receiving signals and have enabled the transmitter for WSPR.

Teensy LC wired up for transceiver support

Addendum:  After investigating a bit more, I discovered that the microphone input level was set way too high in the Windows sound settings.  After setting an appropriate level (around 25), everything is operating nominally.