The Bishop Finally Admitted It Had a Back Lobe
The plot started on a lazy Susan.
Not a metaphor — an actual lazy Susan from the kitchen, the one with the faded Tupperware logo that’s been holding condiments since approximately forever. I’d mounted a small Yagi to it with a hose clamp and a prayer, run coax down through the centre (not through, exactly — draped awkwardly around), and pointed a signal generator at it from across the basement.
Every five degrees. Click the bearing. Log the number. Seventy-two readings per rotation. The half-power beamwidth came out to about 32 degrees, which means this antenna really does throw most of its energy in one direction, with a measly little bulge leaking out the back. Front-to-back ratio of maybe 18 dB. The polar plot looked like a teardrop with ambitions.
And I thought: that’s a bishop.
Not abstractly. Specifically. The shape on my graph paper, if you extruded it into three dimensions and put a flat base on it, would stand on a chessboard and mean something. The bishop moves diagonally, commits to a direction, doesn’t look back. This Yagi — narrow beam, focused intention, token rear awareness — that’s the same energy.
Twenty-seven hobbies in, and apparently I’ve started anthropomorphizing radiation patterns.
The Mapping
Once the idea landed, the rest came fast. A dipole has that classic figure-eight pattern, bilateral and patient — it sees both directions on its axis but ignores the sides. That’s a rook. Straight lines, symmetrical power. The queen should be something with both vertical and horizontal authority: a collinear or stacked array, omnidirectional in azimuth but with real gain. The knight gave me trouble until I remembered loop antennas have that strange L-shaped null pattern, and then it was obvious.
The king gets a ground-plane vertical. Omnidirectional but short. Needs constant protection. Doesn’t move much. I’m not editorializing; that’s just the physics.
What I didn’t expect was how the pawns would work out. A rubber duck antenna — the stubby little thing that comes with every handheld radio — has a nearly spherical pattern with just enough distortion to give it shoulders. Eight of those, slightly undersized, marching across the board. Expendable but functional.
The Measurement Rig
The lazy Susan actually works better than it should. What matters is getting into the far field — past the Fraunhofer distance, where the radiation pattern stabilizes and stops being a near-field mess. For a 2-metre Yagi that’s only about 60 centimetres of boom, I need roughly four metres of separation to get clean readings. The basement is six metres corner to corner, so I’m legal.
I log into a spreadsheet, convert to Cartesian coordinates, and run it through OpenSCAD to extrude the 2D polar plot into a 3D solid. The formula is embarrassingly simple: for each angle θ, the radius r becomes the distance from the piece’s centre axis at height z. Loft those circles together and you get the silhouette.
The first bishop came off the print bed at 11:40 PM. Still warm. The narrow beam became a sharp, almost confrontational nose. The back lobe is there too — a small bulge near the base, the 18 dB of leakage made physical. When I picked it up, I could feel the null. The pinch where the pattern drops to nothing, right at the transition between front and back lobes. My fingers knew it immediately.
There’s a moment in RF Waterfall Lithophanes where I held a frozen hour of spectrum up to a window and watched it glow. This is the same impulse — making the invisible holdable — but rotated 90 degrees. The lithophane froze time on the frequency axis. The chess piece freezes space on the bearing axis. Both start with something I can measure but not see, and end with something I can hold.
What I Hadn’t Considered
The pieces have heft according to their patterns. A dipole-rook, being basically a sphere with a waist, uses more material than the sharp bishop. When you set them on the board, the rook thunks. The bishop clicks. The difference isn’t intentional, but it’s true to the underlying physics — broader patterns mean more plastic, mean more mass.
The king — omnidirectional, squat — is the heaviest piece on the board.
I have one bishop, one pawn, and a lot of measurements left to take. The rook is queued in the slicer. Somewhere around 29,560 games of chess, I’ve held a lot of pieces, and none of them have ever contained an antenna pattern.
Tomorrow these will just be chess pieces. Weird ones, yes. Conversation starters, maybe. But also: real pieces, playable on a real board. The radiation patterns become grips. The nulls become tactile landmarks. The physics of the air, frozen into something I can castle with.
The lazy Susan goes back to holding sriracha. For now.