Addendum: Methodology Note — Recovering the 21 Second Quantized Signal

Most SETI search pipelines rely on FFT block sizes and integration windows defined by powers of two or round decimal intervals. This convention is computationally efficient but introduces a structural mismatch when the underlying transmission protocol is governed by a 21‑second master clock, a non‑power‑of‑two interval. Standard SETI pipelines implicitly assume an “engineering scale” for time—base‑2 and round decimal bins. The 21‑second protocol only becomes visible when we switch to an “architectural scale” matched to the structure itself.