Left panel: real-space correlations (normalized to a comoving separation of 10 Mpc) for the (Φ, Φ), (Φ, δ), and (δ, δ) field combinations as a function of separation from the CMB surface, with density-weighted correlations decorrelating exponentially. Right panel: angular correlation coefficient ρ_ℓ as a function of redshift, field combination, and multipole for full CAMB CMB transfer functions in magenta, with ϕ, δ at ℓ = 2, 20, 70, and SW (ℓ = 70; circles). Extending the observable range to z ∼ 600 (dashed green line) reduces the radial separation from last scattering and increases the coherent multipole range above ℓ_c ≈ 71. The shaded yellow region depicts the typical observable range of an interferometric experiment.