CM ============================================================ CM TRAPPED DIPOLE: 40M / 20M / 10M CM Parallel resonant coaxial traps CM NEC-2 / EZNEC compatible CM CM Architecture (one side, fed at center): CM Feed -> [10M trap at 2.64m] -> [20M trap at 5.26m] -> tip at 10.05m CM CM Trap model: parallel RLC lumped load CM 10M trap: f0=28.5 MHz, L=0.50 uH, C=63 pF, Q=55, Rp=4863 ohm CM 20M trap: f0=14.175 MHz, L=1.23 uH, C=103 pF, Q=77, Rp=8452 ohm CM CM Segments are 1m each for modeling accuracy. CM Wire 1: feed to 10M trap (left), -2.64m to 0 CM Wire 2: 10M trap to 20M trap (left), -5.26m to -2.64m CM Wire 3: 20M trap to tip (left), -10.05m to -5.26m CM Wire 4: feed to 10M trap (right), 0 to +2.64m CM Wire 5: 10M trap to 20M trap (right), +2.64m to +5.26m CM Wire 6: 20M trap to tip (right), +5.26m to +10.05m CM CM Antenna is at 10m AGL, horizontal polarization CM Free space model also included (GE 0) CM CM FREQUENCY COVERAGE: CM 10M: 28.0 - 29.7 MHz (resonant ~28.5 MHz) CM 20M: 14.0 - 14.35 MHz (resonant ~14.175 MHz) CM 40M: 7.00 - 7.30 MHz (resonant ~7.15 MHz) CM CM USAGE: Load in EZNEC or xnec2c. Run frequency sweep for each band. CM Adjust element lengths to fine-tune resonance. CM 10M element adjust: wire 1 and 4 length CM 20M element adjust: wire 2 and 5 length CM 40M element adjust: wire 3 and 6 length CM ============================================================ CE CM --- Geometry --- CM Tag Segs X1 Y1 Z1 X2 Y2 Z2 Radius(m) GW 1 3 -2.64 0.0 10.0 0.0 0.0 10.0 0.00095 GW 2 3 -5.26 0.0 10.0 -2.64 0.0 10.0 0.00095 GW 3 5 -10.05 0.0 10.0 -5.26 0.0 10.0 0.00095 GW 4 3 0.0 0.0 10.0 2.64 0.0 10.0 0.00095 GW 5 3 2.64 0.0 10.0 5.26 0.0 10.0 0.00095 GW 6 5 5.26 0.0 10.0 10.05 0.0 10.0 0.00095 CM --- Ground (real earth, medium: ep=13, sig=0.005 S/m) --- GE 1 CM --- Ground parameters --- GN 2 0 0 0 13.0 0.005 CM --- Excitation at center of dipole (wire 1, segment 2) --- EX 0 1 2 0 1.0 0.0 CM === LOADING CARDS === CM Trap loads modeled as parallel RLC at resonance using series equivalent CM CM LD type 0: Series RLC load R, L, C CM For parallel RLC at resonance, high Rp dominates: model as R load CM More accurate: model as series RLC where Rs=Rp/Q^2, Ls=L, Cs=C CM CM --- 10M TRAPS (RG-213, 30mm former, 7 turns) --- CM f0=28.5 MHz, L=0.50uH, C=63pF, Q=55, Rp=4863 ohm CM Series equiv at 28.5 MHz: Rs=Rp/Q^2=1.61 ohm, Ls=0.50uH, Cs=63pF CM Wire 1 (left), last segment (closest to trap point = seg 3) LD 0 1 3 3 1.61 5.0e-7 6.3e-11 CM Wire 4 (right), first segment (seg 1) LD 0 4 1 1 1.61 5.0e-7 6.3e-11 CM --- 20M TRAPS (RG-213, 50mm former, 7 turns) --- CM f0=14.175 MHz, L=1.23uH, C=103pF, Q=77, Rp=8452 ohm CM Series equiv: Rs=Rp/Q^2=1.43 ohm, Ls=1.23uH, Cs=103pF CM Wire 2 (left), last segment (seg 3) LD 0 2 3 3 1.43 1.23e-6 1.03e-10 CM Wire 5 (right), first segment (seg 1) LD 0 5 1 1 1.43 1.23e-6 1.03e-10 CM === FREQUENCY SWEEP: 10M BAND === FR 0 15 0 0 28.0 0.1 CM === RADIATION PATTERN at 28.5 MHz === RP 0 37 73 1000 0.0 0.0 5.0 5.0 EN CM ============================================================ CM NOTE: Run three separate frequency sweeps for full multiband analysis: CM CM 10M: FR 0 17 0 0 28.0 0.1 CM 20M: FR 0 15 0 0 14.0 0.025 CM 40M: FR 0 13 0 0 7.0 0.025 CM CM EZNEC users: set View Antenna to each frequency after sweep. CM The traps are NOT perfectly modeled at non-resonant frequencies because CM the LD card uses fixed L,C values. For multi-frequency analysis, use CM separate NEC decks with frequency-appropriate trap impedances, or use CM an EZNEC trap model with L and C explicitly. CM CM ADJUSTING ELEMENT LENGTHS (start here for field tuning): CM 10M too high: lengthen wires 1 and 4 CM 10M too low: shorten wires 1 and 4 CM 20M too high: lengthen wires 2 and 5 CM 20M too low: shorten wires 2 and 5 CM 40M too high: lengthen wires 3 and 6 CM 40M too low: shorten wires 3 and 6 CM ============================================================