An interesting test would be to drop the 12S into one of the old noisy boards to see if that already fixes the issue - I don't want to solder these feed thru caps any more often than absolutely necessary ...
And here's the answer. My old gw with l/4 monopole and esp-12e while accessing SPI flash:
Noise level, Percent of detections
-89.5, 10%
-90.0, 10%
-90.5, 20%
-91.0, 10%
-91.5, 40%
-92.5, 30%
-93.0, 10%
-93.5, 40%
-94.0, 10%
-94.5, 30%
-95.5, 60%
-96.0, 30%
-96.5, 40%
-97.0, 20%
-97.5, 40%
-98.0, 40%
-98.5, 40%
-99.0, 50%
-99.5, 50%
-100.0, 70%
-100.5, 30%
-101.0, 50%
-101.5, 80%
-102.0, 80%
-102.5, 40%
-103.0, 50%
-103.5, 80%
-104.0, 90%
-104.5, 40%
-105.0, 50%
-105.5, 40%
Same revision GW, same antenna, but now with ESP-12S, while accessing flash:
Noise level, Percent of detections
-100.5, 20%
-101.0, 30%
-101.5, 80%
-102.0, 100%
MUCH better.
Here's without accessing flash:
Noise level, Percent of detections
-100.0, 10%
-100.5, 20%
-101.0, 10%
-101.5, 80%
-102.0, 90%
-102.5, 100%
So all in all the 12S is a huge improvement. Flash access is no longer an issue. But my other improvements (a) enable using the 12E without impairment and (b) further bring down the remaining noise.
Joe