Chris Freedom flat-plate CT test: opposite-polarity effect spans ~1–16 kHz (broadband); fixed ~120–150 µs droop interval; yellow/blue ratio ~14:1 at two frequencies (extends #3510)

Bench: Chris Freedom, Discord #neuralstan20-testing 2026-11-03, same rig as #3510 (CT secondary, one diode per end, 9 mm flat 304 SS test cell, 30 ppm, 4 V supply, probes vs CT). He reports the opposite-polarity ("EOP") effect across roughly 1–16 kHz. Second 100x probe on order. Two more handheld captures, my reading of the photos. (A) CH1 yellow 200 V/div X100, CH2 blue 20 V/div, 50 us/div: period about 280 us (blue counter 3.648 kHz); yellow max 440 V, Vpp 452 V; blue max 8 V, Vpp 31.6 V. (B) CH1 50 V/div X100, CH2 5 V/div, 50 us/div, photo upside down: period about 175 us (about 5.7 kHz by graticule; the counters' 9.73 and 20.21 kHz are unreliable); yellow max 114.6 V, Vpp 103 V; blue max 1.6 V, Vpp 9.16 V. The shape is the same at 2.1, 3.6 and 5.7 kHz: at onset yellow steps up and blue steps down (differential); both magnitudes droop near-linearly for about 120–150 us, nearly constant across frequency; then both step UP together (common mode); a flatter stretch then shrinks as frequency rises. This is consistent with a fixed-width on-time, magnetizing-current droop through series R, then turn-off. Amplitude falls as frequency rises (yellow max 705, 440, 115 V). The yellow:blue Vpp ratio is 14.3 (#3510), 14.3 (A) and 11.2 (B). A near-constant ~14:1 between two nominally symmetric CT halves looks more like a probe-factor error (10x probe read on an X100 setting) than physics; unconfirmed until the same-point probe check. Broadband 1–16 kHz with no peak argues against LC resonance and toward the cell impedance (9 mm, about 1.9 kohm) no longer clamping the secondary, unlike the coax in #3508.