- Multi-band Dipole / Doublet - described on pages 7-10
- Horizontal Loop - described on pages 16-19
The SWR and impedance results cover the full range from 3.5 to 30 MHz. The last page shows the impedance for selected frequencies within the ham bands. Only the points are plotted on that graph.
Further analysis will compare the SWR and impedance results for 300 ohm and 450 ohm feedlines. I believe that the software can also provide an overall efficiency figure for the combination of feedline and antenna.
Update 7/4/15: Below is a graph of impedance (for the shortened dipole) calculated at selected frequencies within the HF ham bands (3-30 MHz). These points are for the transmitter end of a 300-ohm feedline for 3 different lengths: 1/8 wavelength, 1/4 wavelength and 3/8 wavelength (at 3.5 MHz). The 1/8 and 3/8 wavelength cases correspond to the recommendations of the W8JI article referenced above. I was a bit surprised at the high impedance values for the 3/8 wavelength case in the 75/80 m band, and turned to the venerable Smith Chart to double check the impedance transformation of the 3 feedline lengths. Its results agreed with the results of the NEC software. I can provide a table of the graph data to anyone who is interested.
It was interesting to see that the 1/4 wavelength feeder gave reasonable impedance levels on some of the bands, and that the 1/8 wavelength case was sometimes better than the 3/8 wavelength case. Impedance levels for a 5/8 wavelength feedline should be similar to those for the 1/8 wavelength case.