Antenna Modeling for Radio Amateurs Steve Stearns, K6OIK Northrop Grumman Electromagnetic Systems Laboratory San Jose, California [email protected] [email protected] 1 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Outline (cid:131) History of electromagnetics (cid:131) Computational electromagnetics (cid:190) Method of Moments (MoM) (cid:190) BRACT, WIRA, AMP, NEC 1-4, IE3D, WIPL-D, FEKO (cid:131) Four main programs for amateurs (cid:190) EZNEC (cid:190) 4nec2 (cid:190) WIPL-D Lite (cid:190) FEKO LITE (cid:131) Advanced applications (cid:190) Terrain analysis by MoM (cid:131) References, books, and software 2 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Question for 2008 (cid:131) Is the current the same everywhere along a wire? I I in out ? I = I in out 3 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Answer: It Depends (cid:131) “Yes” for steady-state d-c current (cid:131) “Almost yes” for low-frequency a-c current or short wires (cid:131) But “no” for high-frequency a-c current because electrons can bunch up (cid:131) J.C. Maxwell found a way to make the answer yes ∂D I ∇×H = J + I in out ∂t ⎛ ∂D⎞ 0 = ∫∫⎜J + ⎟•dS ∂t ⎝ ⎠ S ∂ I −I = ∫∫D dS in out n ∂t S 4 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 History 5 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Who Does Not Belong in this Picture? 6 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Answer: Leonardo Da Vinci and Isaac Newton Leonardo Da Vinci Andre-Marie Ampere Michael Faraday 1452-1519 1775-1836 1791-1867 James Clerk Maxwell 1831-1879 Isaac Newton Carl Friedrich Gauss Georg Simon Ohm 1642-1727 1777-1855 1789-1854 7 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 The Maxwellians George Francis FitzGerald Oliver Heaviside Oliver Joseph Lodge 1851-1901 1850-1925 1851-1940 Heinrich Rudolph Hertz John Henry Poynting 1857-1894 1851-1914 8 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Heaviside’s Vector Equations for Maxwell’s Theory ∂B ∇ × E = −M − ∂t ∂D ∇ × H = J + ∂t ⋅ ∇ D = ρ e ⋅ ∇ B = ρ m D = εE J =σ E e B = μH M =σ H m “And God said, Let there be light; and there was light.” Genesis 1:3 9 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008 Key Dates in Antennas 1842 Discovery of radiation – J. Henry 1873 Treatise on electrodynamics – J.C. Maxwell 1875-87 Early radiation demonstrations: Edison 1875; A.E. Dolbear 1882; H. Hertz 1887 1889-06 Phased arrays – S.G. Brown, J.E. Murray, Artom 1895-01 Radio communication, fan dipole, polar plots – G. Marconi 1897 Biconical dipole, loading coil, tunable LC matching network, counterpoise, “impedance” – O.J. Lodge 1907 Goniometer, electrical steerable array, radio direction- finding – Bellini & Tosi 1907 Ground losses, ground waves – Zenneck 1923 Wave-tilt antenna – H.H. Beverage 1928 Endfire array with parasitic elements – Yagi & Uda 1947 Polyrod antenna – G.E. Mueller and W.L. Tyrell 10 S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008