CM 144 MHz 2 Stacked Halo Antennas at 0.5 and 1.0 lambda NEC model by Carol F. Milazzo, KP4MD CM Horizontal orientation (using GH command) CM Frequency = 145.000 MHz CM 26-side polygon (40 inch loop with 1.5 inch gap) CM Simulated good ground CM http://www.qsl.net/kp4md/omnihoriz.htm CE SY frq=145 'Input frequency MHz SY cir=40.21493 'Input loop circumference inches (loop + gap) SY r=0.5*cir/3.1415926 'Calculate loop radius SY dia=0.25 'Input loop wire dia. inches SY rad=0.5*dia 'Calculate loop wire radius SY n=26 'Input n-side polygon of loop + gap SY h=40.87 'Input height inches to 0.5 lambda SY g=1.5 'Input gap size in inches SY gseg=int(n*g/cir+0.5) 'Calculate gap length in segments GH 1 n-gseg 1e-300 1e-300*(n-gseg)/n r r r r rad 'First loop GM 0 0 0 0 gseg*180/n 0 0 h 1 'Raise loop to 0.5 lambda GM 1 1 0 0 0 0 0 h 1 'Copy to second loop at 1 lambda GS 0 0 0.0254 GE 1 LD 5 0 0 0 58000000 '0.25 inch copper tubing GN 2 0 0 0 4 0.01 EK EX 0 1 (n-gseg)/2 0 0.5 0 0 'Feed point EX 0 2 (n-gseg)/2 0 0.5 0 0 'Feed point FR 0 0 0 0 frq 0 EN