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CM 2-Element Endfire Phased Array — 20M (14.175 MHz)
CM TM-HYB-001 Rev A
CM
CM Two half-wave dipoles separated by λ/4 (5.29 m)
CM Element 1: 0°, Element 2: −90° (quadrature hybrid feed)
CM Height: 10 m above average ground (σ=0.005, εr=13)
CM
CM Expected pattern: unidirectional cardioid (endfire)
CM Front-to-back ratio: ≈10–12 dB theoretical
CM Gain: ≈5.2 dBd over single dipole
CM
CM Feed network: 90° quadrature hybrid coupler (TM-HYB-001)
CM  Port 1 (input): RF source, 50Ω
CM  Port 2 (0° out): Element 1 via λ/2 50Ω coax
CM  Port 3 (−90° out): Element 2 via λ/2 50Ω coax
CM
CM Coordinate system:
CM  X-axis: element separation direction
CM  Y-axis: along elements (wire axis)
CM  Z-axis: height above ground
CM
CM Endfire direction: +X axis
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CE

CM === ELEMENT 1 (0°, at x=0) ===
CM Half-wave dipole: length = 0.495 × λ = 0.495 × 21.145m = 10.47m
CM Wire: 2mm diameter copper (#14 AWG equivalent)

GW 1 21 0.000 -5.235 10.000 0.000 5.235 10.000 0.001
CM  Tag=1, Segs=21, x1=0,y1=-5.235,z1=10m, x2=0,y2=+5.235,z2=10m, rad=1mm

CM === ELEMENT 2 (−90°, at x=λ/4=5.29m) ===
GW 2 21 5.292 -5.235 10.000 5.292 5.235 10.000 0.001
CM  Tag=2, Segs=21, λ/4 spacing = c/(4×14.175e6) = 5.292 m

CM === GROUND: Average (σ=0.005 S/m, εr=13) ===
GE 1
GN 2 0 0 0 13.0 0.005

CM === EXCITATIONS ===
CM Element 1: magnitude=1, phase=0°
EX 0 1 11 0 1.0 0.0
CM Element 2: magnitude=1, phase=−90° (quadrature hybrid)
EX 0 2 11 0 0.0 -1.0
CM Note: (0.0 + j×−1.0) = 1∠−90°

CM === FREQUENCY ===
FR 0 1 0 0 14.175 0

CM === RADIATION PATTERN (azimuth and elevation) ===
CM Azimuth sweep at elevation 20° (typical low-angle DX)
RP 0 1 361 1000 20.0 0.0 1.0 1.0

CM Elevation sweep in endfire direction (phi=0°)
RP 0 91 1 1000 0.0 0.0 1.0 1.0

EN

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CM EXPECTED RESULTS:
CM   Gain (endfire, 20° el): approximately 7.5 dBi (≈5.5 dBd)
CM   F/B ratio:              ≈10 dB
CM   Main lobe azimuth:      0° (endfire, +X direction)
CM   Feed impedance element 1: ≈ 50-j25 Ω (mutual coupling)
CM   Feed impedance element 2: ≈ 50-j25 Ω
CM
CM MUTUAL COUPLING NOTE:
CM   λ/4 spacing causes significant mutual coupling.
CM   Feed impedance ≠ free-space dipole (73Ω).
CM   Use current-forcing feed method OR add matching network.
CM   Quadrature hybrid provides inherent port isolation which
CM   forces equal currents regardless of element impedance variation.
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