Original configuration

Signal to harmonics: ~10 dB. Signal to "floor": ~20 dB.

Change C7/C8 divider from 33/220 pF to 150/1000 pF Scope shows signal at XTAL1. (DC offset was due to scope mis-calibration.)

Signal to harmonics: ~10 dB. (Lower density of harmonics.) Signal to "floor": ~20 dB.

Added resistive probes to measure clock phase (5 kΩ on "yellow" CLK, 500 Ω on "blue" CLKM)

Signal to harmonics: ~15 dB. Signal to "floor": ~23 dB.

Disabled CLKM

Density of harmonics decreases further.

Added 10 kΩ in parallel to C8 Scope shows averaged signal at XTAL1.

Note: changed FFT ref level.

Added 0.5 pF bypass to antenna feed (at "knee")

No perceptible change.

Change C7/C8 divider from 150/1000 pF to 220/1000 pF Scope shows average signal at XTAL1.

No significant change.

Commands used in all cases:

atrf-txrx -f 2450 -p 3 -T -0.5  
atrf-txrx -f 2450