Coil Inductance and Q Calculator

[k6sti]

The program now accounts for radiation loss when calculating coil Q. You can include radiation as a small loop, as a short Hertzian dipole, both, or neither. Some coil radiation may be beneficial and you can exclude it from the loss calculation. An example is an antenna loading coil where incidental dipole coil radiation augments that from the antenna.

When I rechecked my program calibration set (coils carefully measured with an HP 4342A Q meter), the average error magnitude for Q dropped when I included both radiation types. This convinced me that coil radiation loss is significant. I was surprised because I had not checked any coil above 25.2 MHz. Coil radiation is much greater at VHF where dimensions in wavelengths are larger than at HF. But evidently HF dimensions are large enough to cause measurable coil radiation.

The optimizer handles radiation automatically. For example, dipole radiation is proportional to the square of coil length and is sensitive to that dimension. With dipole radiation enabled, the optimizer will find shorter coils when maximizing Q because the longer ones have a radiation loss penalty.

http://ham-radio.com/k6sti/coil.htm

Brian