Statistical resolution limit (SRL) — closest two targets tellable apart vs SNR · hover a point (session 014z DF model)
9.30 dBi · F/B 15.6 dB · F/WORST-3D-LOBE 14.2 dB @915 (max lobe anywhere behind the x=0 plane, full-sphere scan — the DF ambiguity headroom) (14.1/15.6/16.4 across 895/915/935 — the F/B skirt rises with falling res; the deep null sits ~50 MHz above resonance so 915 rides its skirt) · KEY DF FINDING: the horizon-plane (az) rear null and the 3D-worst-lobe are ANTI-CORRELATED — closing the Moxon gap C deepens the az null (F/B@915 14.5→15.6→16.8→17.8 as C 18.5→17.5→16.5→15.5) but pumps a +70°-ELEVATION rear lobe, so F/worst-3D-lobe FALLS 14.5→14.2→13.6→13.2; loose C is best for full-3D DF rejection, tight C for a near-horizon 2D F/B spec. SHIP (C 17.5) recovers the 3 mm-apron rev-B az-F/B while keeping the 3D lobe at the horizon · S11 -19.7 dB @915 (Zin 61+4j — direct 50Ω, no matching network) · vs the AS-ORDERED a915_4el_final it is based on (same rig, PML_8 port-at-neck: 9.08 dBi · F/B 10.4 (10.1/10.4/11.4) · F/worst-3D 10.4 · S11 -32.5): +0.22 dB gain, +5.2 dB F/B, board 179.4→131.5 mm tall (-27% area) · MOXON bend on the ordered board: reflector 130.5 straight + 15 mm tips folded FORWARD 12, driven 107 tip-to-tip + tips folded BACK 21, coupling gap C 17.5 mm kept FR4-free (the gap rail is ONE 6 mm diagonal band, reflector apron -> driven apron, no pocket; CONSISTENT 0.5 mm JLC-min apron around reflector AND driven (routed-outline copper-to-edge 0.3 min, ±0.2 tol → 0.5 recommended), boom kept; r1 fillets = router min) · directors, spacings, GCPW feed, 58 mm reflector-shorted slotline balun and the BACK-MOUNTED CONNECTOR unchanged from the ordered board: 4-leg flange SMA THT on the BOTTOM of the rear tail tab, pin (3.97, 8.0) drill 1.2, legs 1.4 on a 5.0 mm square, M3 mounts (0,0)/(0,28) — coax centre = SMA pin → GCPW → neck → +y arm; shield = flange legs → stitched tail pour → reflector · solder points + balun drawn in the feed schema; fab zip parses clean (gerbonara) · Gerber + STEP + DXF (CST Studio 2024-ready: import the STEP as solids — FR4 + both copper layers, drills cut — or the layered DXF — BOARD/COPPER_TOP/COPPER_BOT/DRILL/PORT — and extrude; CST_README in the zip has the steps + the 50Ω discrete-port placement across the slot at the neck) · ALTERNATE dims on the same board (one-knob swaps, PML-verified): match-optimal l_drv 109 / l_refl 128 / tip_back 19 → S11 −32.3 dB (VSWR 1.05), 9.41 dBi, F/B 12.2 (F/worst-3D 12.3); max-horizon-F/B tip_back 22 (C 16.5) → az-F/B 16.8, F/worst-3D 13.6, S11 -16.7 (near-horizon emitters) · every PML final stores its FULL-SPHERE 3D result (D(θ,φ) + S11/Zin curves + params) on the antenna-sim-cache Modal volume for reuse — monopulse pairing / DF templates / re-scored metrics without re-solving (a915_moxon.py::cache_ls, ::cache_get) · MUR ladders s1–s4 (35 s/run, 2-CPU containers) + PML_8 finals; az-cut worst-rear ±60° 15.6 dB
⬗ stack-up: FR4 1.6 mm (εr 4.3) · 1 oz Cu · 2-layer, via-stitched (Ø0.5) · rounded r2 outline, hugged ribs + diagonal gap rail, moxon gap FR4-free · rear-tab SMA (bottom face)