Nonresonant Dipole
What is a non-resonant dipole? Well, a non-resonant dipole is basically an antenna (Di-pole or Two-pole) that might not have a resonance (X=0) point on any of the frequencies you would like the antenna to operate. Sounds difficult? Nope it isn't, G5RV (Louis Varney) and ZS6BKW (Brian Austin) have presented us with this type of Antenna. They make the Antenna x meter long and use a high impedance (high Z) feed line (ladder line, twin lead) to create a TLT aka a Transmission Line Transformer to bring the impedance in the range of our TRX impedance.
However, a non-resonant dipole does NEED AN ATU (Antenna Tuning Unit). Since ATU's find it very hard to tune High Voltage Nodes (High Z) at the feed point the following Spreadsheet might help avoid building antennas that have one or more such nodes.
NOTE: This is a rough calculation and does NOT take in to account ground and other losses. But, it might be of use if you are going to build a non-resonant dipole.
Insert your antenna length into the cell "Antenna length in meters", then insert the Feed line length into the "Feed line length in meters" cell and last the velocity factor of the feed line into the "Velocity factor of Feed line" cell. The sheet calculates the radiator length (½ of the antenna) and it also calculates the total length of the radiator and feedline, both in degree and wavelength. As we would like to avoid high Z (Voltage feed) areas of the antenna, the sheet will highlight cells if the feed point is within + - 5% of a VOLTAGE FEED.
Some Velocity Factors :
300 Ω ladder line ≈ 0.82
450 Ω ladder line ≈ 0.91
Home build ladder line ≈ 0.97